Don't Kill Your Engine!

[Big Jay D]

It would be cool to have a 2 speed transmission. Not one that shifts on the fly but like was stated above. Low gear to spin the prop slower at a high rpm and a high gear for higher speeds. Then you can run a shallow prop for surfing and just hangs the drive ratio for everything else.

[shawndoggy]

I never rode in one but from what I understand left some engineering or execution to be desired. Think loud clunk.

It's my understanding (never having been in a boat with one or experienced it myself) that there's a technique to shifting the 2 speeds smoothly, and that it can be done, but requires a rev match to go along with the shift to avoid the clunk.

[jkendallmsce]

It's my understanding (never having been in a boat with one or experienced it myself) that there's a technique to shifting the 2 speeds smoothly, and that it can be done, but requires a rev match to go along with the shift to avoid the clunk.

Maybe they could install some paddles on the steering wheel, like on some of the high performance cars like the vettes, porsches, etc.. Now that would be slicker than dog poop first thing in the morning.

That would be like taking a NASCAR car and making it into a F1 racing machine!!!

[nemalibu]

If you wakeboard or wake surf and load your boat heavily it is critical that your boat is propped appropriately to ensure that your engine gives you the kind of life that you expect. It is critical that the engine is able to turn RPM at wide open throttle within the designated range for your engine. The standard 5.7L engine, like the LCR … the engines that have the flame arrestor at the top of the engine like a carbureted engine … the WOT RPM range is 4600-4800. The premium 5.7L engine, The Monsoons … the engines that have the flame arrestor at the rear of the engine and a decorative plenum on top … the WOT RPM range is 4800-5200. The 6.0L and 6.2L engines … the LS3, the L96 and the LSA … the WOT RPM range is 5200-5600.

What you need to do is load the boat the way you would for whatever activity you are loading it for. If that means all standard ballast full, extra ballast, 3 cases of cold beverages and 8 friends … load it up. Make sure your fuel tank is full also. You want the boat to be the heaviest that it is ever going to be. Now carefully take the boat up to wide open throttle and see what the maximum engine RPM is. Be careful because the added weight might make the boat handle differently at WOT than it does when lightly loaded.

If the RPM for your engine is within the WOT RPM range for the engine you are “GOLDEN”. Go wakeboarding … go surfing … have fun. If the engine turns RPM at WOT it means that it will be properly loaded throughout the RPM range. You don’t always have to run the engine at WOT … in fact I don’t recommend that you run at WOT for extended periods of time … it just has to be able to run within that range at WOT. If the engine is not able to turn in the WOT RPM range for your engine, you have two choices … take some weight out of the boat or change the propeller. Every time you run the boat in those same conditions (overloaded) you are risking the longevity of your engine, and if the engine fails under those conditions it is a good chance the failure would not be covered under warranty even though it may be within the warranty period.

If you can’t tolerate reducing the weight in the boat, you will have to re-prop with a smaller pitch/diameter propeller to reduce the load on the engine. I am not a prop expert so I won’t be able to help you select the correct prop. Fortunately, I have some friends who are experts. You can contact the good folks at ACME (www.acmemarine.com) or OJ (www.ojprops.com). Either of those fine companies will be able to help and make propeller suggestions that will get you where you need to be RPM wise.

Once you are propped for the maximum load in the boat, what is going to happen when you run the boat without the load? Not to worry … running the boat under-propped for the load may have an effect on the WOT performance of the boat … it probably won’t go as fast. You won’t have to worry about over-revving the engine though because all of our fuel injected engines have RPM limiters that will not allow the engine to over-rev. It is much better for your engine to be under-propped than it is to be over-propped. If you don’t like the lightly loaded boat performance with the smaller prop, keep your old prop and use it when you are running lightly loaded and switch to the heavy load prop when you use the boat heavily loaded.

Why is this so important? For example, if your engine is only able to turn 4000 RPM at WOT, the engine is running hot and hard but because it cannot turn at the rated RPM, the water pump is not pumping as much water as it should be or that the engine wants when it is working that hard. Also, under those conditions, the throttle settings are telling the ECM/computer to supply fuel to the engine for WOT operation but because the engine is not turning the appropriate RPM, the engine is over-fueled. It may not be able to burn that excess fuel … so now we start washing oil from the cylinder walls which accelerates cylinder wear. And where does that excess fuel go? Some goes past the rings into the oil which dilutes the oil and reduces its ability to properly lubricate the engine … and some goes out through the exhaust. If the engine has catalytic converters, unburned gasoline in the catalysts creates extra heat in the catalyst and with the diminished water flow because of reduced engine RPM we have a hard time keeping the catalysts and manifolds cool which creates more problems.

Bottom line … it is extremely critical that your engine is able to run within the rated RPM range at Wide Open Throttle. If you run your boat heavily loaded and the engine will not turn within the designated RPM range, you are killing your engine and if it dies under those conditions that is considered abuse and abuse is not covered by warranty.

The Engine Nut has spoken! Let the flames begin!!

How do you do this test with the wedge down? Under those conditions my boat would likely exceed the max allowed speed for the wedge down condition.

[Michigan boarder]

I think another question is at what rate does that damage occur. So that if you miss your RPM mark by 400 RPM, how much damage are you doing, versus if you are spot on, versus if you miss it by 800 RPM, etc. Then you can start to quantify the life you are taking out of the engine and put a price to it. Then you can decide whether it is worth re-propping and what sports are best for your boat.

For instance, there's me. 265hp Echelon LX with the original 13x13 prop. In order of desending speeds, we barefoot, ski, tube, wakeboard and wakesurf this boat. In my case I don't think there's a prop for my boat that will run the range from barefoot to surf. Probably not for any boat, for that matter. In fact, as I'm writing this I don't think I even want to know the cost. I'm going to do all that stuff with the boat regardless. If the engine goes in a few years, I'll replace it. But I'm not giving up barefooting, and my wife isn't giving up surfing.

Still, it's a great study and write up you did E.N., good information.

[UWSkier]

You know, there used to be companies that made variable pitch props for OBs and SDs. I know they have a lot more hub space to work with, but I wonder if those principles could be applied here at all. Use cams and weights to shift the prop above a certain speed, and make the internals interchangeable so owners could tune when the shift happens. That or make it quickly adjustable with a wrench or something and rather than relying on cams, just let the owner select if they want the blades locked in the power or speed setting. No shifting underway that way.

Edited July 24, 2012 by UWSkier

[Nitrousbird]

For example, if your engine is only able to turn 4000 RPM at WOT, the engine is running hot and hard but because it cannot turn at the rated RPM, the water pump is not pumping as much water as it should be or that the engine wants when it is working that hard.

I did a bit more research so I could have a few numbers before commenting on this.

My example: The Calloway 383 LT1 (an Indmar motor) put in the 1996 - 1999 Corvette boats. The stock, LT1 mechanical water pump flows 66 GPM. But Indmar chose to use the CSI electric water pump (have one on my LT1 - good water pump), which flows a constant 37 GPM.

BUT - the CSI only flow a little over half what the stock pump does, so if there was a cooling issue due to waterpump flow at lower RPM/higher loads, then the Calloway must overheat every time you run even a light load with the correct prop as it would be running WOT at the proper RPM, but not getting the proper water flow due to running a lower volume electric water pump. I am better this isn't the case, but disproves the theory.

In road racing, the CSI pump isn't a good choice and is why those guys stick with the mechanical pump. But in boats, instead of having a small air-to-water cooling of a radiator, you have a much better water to water cooling, and the radiator is the entire lake.

Further, on those running super heavy loads and underpropped, has anyone actually seen an increase in running temp?

[snowrider]

Appreciate the information. Tried this today on our 07 VRide. 200lbs lead in front, 500lb mid ballast and rear ballast filled approx 400lbs each out of 750lbs ProSac. Full tank gas. 3ppl which is typical. WOT was 4700rpm. Didn't try it with our surf setup but we rarely surf with any more weight just adjusted around the boat.

[Smeltz]

I am a simple boat owner. Don’t understand WOT. Also my lsv has the 383 hammerhead motor. When we have all factory ballasts full, with extra ballast in the front (250lbs) and two other extra  ballasts in each back corner with  (400lbs) in each side with the wakeshaper on one side and 6 adults.  The boats RPM’s are at 3100-3400. Is this the desired RPM? What is the desired rpm under full load (with full tank of fuel  ballasts, extra ballasts friends, & 🍻’s) we only surf. 

[MLA]

2 minutes ago, Smeltz said:

I am a simple boat owner. Don’t understand WOT. Also my lsv has the 383 hammerhead motor. When we have all factory ballasts full, with extra ballast in the front (250lbs) and two other extra  ballasts in each back corner with  (400lbs) in each side with the wakeshaper on one side and 6 adults.  The boats RPM’s are at 3100-3400. Is this the desired RPM? What is the desired rpm under full load (with full tank of fuel  ballasts, extra ballasts friends, & 🍻’s) we only surf. 

What prop are you running? This impacts RPM

[Smeltz]

1 minute ago, MLA said:

What prop are you running? This impacts RPM

The stock one l believe. What ever came in a 2005 lsv 383 hammerhead.

[justgary]

2 hours ago, Smeltz said:

I am a simple boat owner. Don’t understand WOT. Also my lsv has the 383 hammerhead motor. When we have all factory ballasts full, with extra ballast in the front (250lbs) and two other extra  ballasts in each back corner with  (400lbs) in each side with the wakeshaper on one side and 6 adults.  The boats RPM’s are at 3100-3400. Is this the desired RPM? What is the desired rpm under full load (with full tank of fuel  ballasts, extra ballasts friends, & 🍻’s) we only surf. 

WOT = wide open throttle. 

Your prop is essentially like a single gear in a car transmission, so engine nut is saying that you need to choose that gear wisely or risk overloading your engine.  The only real option to a drastically variable load is to change the prop. 

Regards, 

- Just Gary 

[Smeltz]

17 hours ago, justgary said:

WOT = wide open throttle. 

Your prop is essentially like a single gear in a car transmission, so engine nut is saying that you need to choose that gear wisely or risk overloading your engine.  The only real option to a drastically variable load is to change the prop. 

Regards, 

- Just Gary 

Thx for the help. But still don’t know if I am running at the right rpms or are they to high?

[justgary]

I think the whole point of this thread is that you can't get RPM too high, only too low.  

Re-read the original post and then determine your max RPM at WOT with a full load (the biggest load you will ever have).  If you are in range, you are good.  If you are low, you need a new prop. 

[williemon]

For my engine, its 4600 to 5200 rpm for the wide open throttle range. With no load i can run 5200 give or take about 100 rpm. Thats good to go. When loaded, i need to make sure i can run at least 4600 rpm. If not, then i need to have the prop tweaked or repropped to be able to hit at least 4600 rpm. In this way i am not lugging the engine. That may mean that while not loaded i may bounce off the rev limiter a lot if i let it, but i wont be lugging the engine. It is a trade off. You have to prop for what you do most. Id love to have a two speed tranny. Make it low and high. Low will run 25 to 30 at 5200 rpm, while the high would run up to 45 to 48 at 5200 rpm. You select low or high prior to putting it in gear and then you leave it there for that activity. Low for wake boarding and surf. High for foot, ski, tube, kneeboard. I had to prop my old I/O for pulling power since it just had 130 hp . I could pull hard but top speed was 35 mph at 4600 rpm which was top rpm for that year 3.0L. It would over rev easy so i had to be careful. 

[SkiPablo]

On 7/22/2012 at 12:02 PM, Engine Nut said:

If you wakeboard or wake surf and load your boat heavily it is critical that your boat is propped appropriately to ensure that your engine gives you the kind of life that you expect. It is critical that the engine is able to turn RPM at wide open throttle within the designated range for your engine. The standard 5.7L engine, like the LCR … the engines that have the flame arrestor at the top of the engine like a carbureted engine … the WOT RPM range is 4600-4800. The premium 5.7L engine, The Monsoons … the engines that have the flame arrestor at the rear of the engine and a decorative plenum on top … the WOT RPM range is 4800-5200. The 6.0L and 6.2L engines … the LS3, the L96 and the LSA … the WOT RPM range is 5200-5600.

What you need to do is load the boat the way you would for whatever activity you are loading it for. If that means all standard ballast full, extra ballast, 3 cases of cold beverages and 8 friends … load it up. Make sure your fuel tank is full also. You want the boat to be the heaviest that it is ever going to be. Now carefully take the boat up to wide open throttle and see what the maximum engine RPM is. Be careful because the added weight might make the boat handle differently at WOT than it does when lightly loaded.

If the RPM for your engine is within the WOT RPM range for the engine you are “GOLDEN”. Go wakeboarding … go surfing … have fun. If the engine turns RPM at WOT it means that it will be properly loaded throughout the RPM range. You don’t always have to run the engine at WOT … in fact I don’t recommend that you run at WOT for extended periods of time … it just has to be able to run within that range at WOT. If the engine is not able to turn in the WOT RPM range for your engine, you have two choices … take some weight out of the boat or change the propeller. Every time you run the boat in those same conditions (overloaded) you are risking the longevity of your engine, and if the engine fails under those conditions it is a good chance the failure would not be covered under warranty even though it may be within the warranty period.

If you can’t tolerate reducing the weight in the boat, you will have to re-prop with a smaller pitch/diameter propeller to reduce the load on the engine. I am not a prop expert so I won’t be able to help you select the correct prop. Fortunately, I have some friends who are experts. You can contact the good folks at ACME (www.acmemarine.com) or OJ (www.ojprops.com). Either of those fine companies will be able to help and make propeller suggestions that will get you where you need to be RPM wise.

Once you are propped for the maximum load in the boat, what is going to happen when you run the boat without the load? Not to worry … running the boat under-propped for the load may have an effect on the WOT performance of the boat … it probably won’t go as fast. You won’t have to worry about over-revving the engine though because all of our fuel injected engines have RPM limiters that will not allow the engine to over-rev. It is much better for your engine to be under-propped than it is to be over-propped. If you don’t like the lightly loaded boat performance with the smaller prop, keep your old prop and use it when you are running lightly loaded and switch to the heavy load prop when you use the boat heavily loaded.

Why is this so important? For example, if your engine is only able to turn 4000 RPM at WOT, the engine is running hot and hard but because it cannot turn at the rated RPM, the water pump is not pumping as much water as it should be or that the engine wants when it is working that hard. Also, under those conditions, the throttle settings are telling the ECM/computer to supply fuel to the engine for WOT operation but because the engine is not turning the appropriate RPM, the engine is over-fueled. It may not be able to burn that excess fuel … so now we start washing oil from the cylinder walls which accelerates cylinder wear. And where does that excess fuel go? Some goes past the rings into the oil which dilutes the oil and reduces its ability to properly lubricate the engine … and some goes out through the exhaust. If the engine has catalytic converters, unburned gasoline in the catalysts creates extra heat in the catalyst and with the diminished water flow because of reduced engine RPM we have a hard time keeping the catalysts and manifolds cool which creates more problems.

Bottom line … it is extremely critical that your engine is able to run within the rated RPM range at Wide Open Throttle. If you run your boat heavily loaded and the engine will not turn within the designated RPM range, you are killing your engine and if it dies under those conditions that is considered abuse and abuse is not covered by warranty.

The Engine Nut has spoken! Let the flames begin!!

Larry is speaking the truth - I have done this on my boats and I actually get better fuel economy when propped to the upper end of the WOT range.

[dshack]

This thread has me rethinking my prop situation. I have a 2019 22LSV w/ 409 at ~6K elevation running a OJ 950 (15 x 13 with .130 cup). When weighted for surfing I am very close to or at WOT throttle but I'm only at 4000 RPMs. The engine "feels" like it is almost being lugged. It seems like I should reprop for something with a lower pitch so that I can reach closer to 5000 RPMs, correct?

Eric at OJ recommended going to a 1922 (15 x 12.5, .120 cup) and Acme recommended a 3093 (15 x 12.5, .165 cup). 

Oh and long term solution = upgrade to a boat with a bigger engine, I know! Or convince the rest of my crew to give up surfing and join me in Foiling w/ no ballast!

[hawaiianstyln]

just now seeing this write-up and can't believe all these years I missed it somehow.  When I blew my motor labor day last year, I was going WOT for about 12-15 minutes solid.  Just before the Rev Limiter would always kick in at 5,500 RPM so basically i was right around 5,400-5,500 for that long.  I never thought anything about it being a concern and now knowing that my WOT safe range is actually 4,800-5,200, I guess I was not operating at safe range then.  Lessons learned.

08 Monsoon 340, 825 hours basically "BLEW UP" my piston and shoved everything down and out the side of my oil pan at 5,500 RPM.  Pretty scary witnessing this.  Basically thought I was on fire as the hot oil blew out and all over the engine bay making it smoke like crazy.  Now I could be wrong and maybe the previous two owners of my boat just treated it like hell or the first owner didn't break the engine in correctly.  I'll never know true root cause unfortunately as MichiganMotorz dissects the core return they don't tell you what may have cause the catastrophic failure.  I wish they did because I'm a cyber security & forensic guy and everything is based off Root Cause Analysis.  It's killing my OCD, but it may have been due to my WOT operating and RPMs...???...

Edited May 23, 2023 by hawaiianstyln

[stang233]

Maybe I am gentle on mine but I try to never take it over 4k rpm. I seem to get everything I need around 3500-3800 even tubing. 

[hawaiianstyln]

13 minutes ago, stang233 said:

Maybe I am gentle on mine but I try to never take it over 4k rpm. I seem to get everything I need around 3500-3800 even tubing. 

well I won't be getting near WOT anymore

[uk_exile]

www search of engine rpm and stress on internal components resulted in the below info. Basically exceeding the manufacturer upper rpm limit is exponentially not good!

The relationship between engine RPM and stress on internal components is not necessarily a perfect square law. However, it's not uncommon for the stress on engine internal components to increase exponentially or follow other polynomial equations as RPM increases. Additionally, the exact relationship between stress and RPM can vary greatly depending on the specific engine design, materials used, operating conditions, maintenance history, and various other factors. So while there may not be a simple square law to describe this relationship universally, it's safe to say that as RPM increases, so does the stress on engine internal components in most cases.

 

 

[JasonK]

How much does this apply to older carbureted engines, with no ECM or catalytic converters?

[oldjeep]

5 minutes ago, JasonK said:

How much does this apply to older carbureted engines, with no ECM or catalytic converters?

There is always a specified WOT range for marine engines (or any engine really).  Don't exceed it.

In the old days before surfing, you would just prop the boat for WOT.  Now that people add thousands of pounds to try to sink the boat you need to be aware that when you have propped for max ballast that you are not exceeding the WOT range when not loaded.

[uk_exile]

Weighted boat is like a car always climbing a very steep hill, whereas unweighted boat is like on driving on moderate hill. Boat engines never get an easy load like car engines on flat do.

[CaptainMorgan]

On 7/24/2012 at 10:56 AM, Michigan boarder said:

I think another question is at what rate does that damage occur. So that if you miss your RPM mark by 400 RPM, how much damage are you doing, versus if you are spot on, versus if you miss it by 800 RPM, etc. Then you can start to quantify the life you are taking out of the engine and put a price to it. Then you can decide whether it is worth re-propping and what sports are best for your boat.

i just re-discovered this thread - super interesting but never saw any comments/answers to the "how close is close enough" question posed...any engine smart guys want to comment?  

For instance, my PCM 409 says WOT should be 5400-5600.  I tried switching to a 17" pitch prop this year as an experiment from the original 15.5" 3077.  This week i tried the suggested worst-case scenario test (hot/humid day + full ballast + lead + gear + people + deployed bimini + boards in racks + 1/2 ft chop) -- and i saw 5000rpm...which is 'only' a few hundred rpm shy of ideal.  The 3077 would probably add a few hundred RPM and be dead on the recommendation, but the 17" prop gives a few mph top end that we enjoy when zipping to/from our favorite spots (no ballast typically). 

Is 5000rpm close enough for an engine 7 years newer than this thread?  That's my hope, but I have the other prop, no cost/big deal to change it back just curious for feedback from those who know engines better than me.  (side note: fuel consumption this season looks ~10% higher than last year at the pump, but that could be within error bars of what activities/who i've been boating with - no scan gauge to give instantaneous readings)