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Engine Nut

Don't Kill Your Engine!

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Nitrousbird

The cooling aspect makes sense to a point, but the Air to Fuel ratio doesn't. The motors are equiped with a MAP sensor, so the ECM should compensate for load vs. RPM and adjust the fuel accordingly.

In the automotive world (where I am more familar with ECM programming) the ECM has tables for both open and close loop operation. In open loop (such as WOT applications), you program the fuel graph based on load vs. RPM. This is why tuning on a load dyno is so useful, as you can hit more of the load cells and tune your A/F ratio accordingly.

I would sure "hope" Indmar tunes their ECM on a load dyno, especially since constant loads are far more common in a boating application. Basically, if a properly running motor is overloaded and only running 3800RPM WOT, the ECM should be compensating the fuel rate to not allow the motor to run super rich.

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Engine Nut

The cooling aspect makes sense to a point, but the Air to Fuel ratio doesn't. The motors are equiped with a MAP sensor, so the ECM should compensate for load vs. RPM and adjust the fuel accordingly.

In the automotive world (where I am more familar with ECM programming) the ECM has tables for both open and close loop operation. In open loop (such as WOT applications), you program the fuel graph based on load vs. RPM. This is why tuning on a load dyno is so useful, as you can hit more of the load cells and tune your A/F ratio accordingly.

I would sure "hope" Indmar tunes their ECM on a load dyno, especially since constant loads are far more common in a boating application. Basically, if a properly running motor is overloaded and only running 3800RPM WOT, the ECM should be compensating the fuel rate to not allow the motor to run super rich.

We do our ECM calibrations on a dyno. We calibrate using a standard prop load curve that is based on the engine operating within a specific operating range at WOT so the calibrations are tuned to that curve from idle to WOT. I am not a calibration engineer but I have been in the industry a long time ... from outboards to stern drives to inboards and one constant that has been there through my whole career is that the engine needs to run within a particular RPM range at wide open throttle to be properly loaded throughout the range of operation.

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LJboater

Still doesn't make senses. Your trying to say the computer will not compensate for the increased load "vs" lower air intake rate. You would be way under the 14.7 to 1 desired ratio

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edwin

it makes perfect sense to me - put the correct prop on your boat to compensate (if req'd) for the load you're putting on the engine.

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shawndoggy

it makes perfect sense to me - put the correct prop on your boat to compensate (if req'd) for the load you're putting on the engine.

It may, but boy oh boy is that a big shift in conventional wisdom. And even "propped," I'm sure a lot of boats won't redline.

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Engine Nut

Still doesn't make senses. Your trying to say the computer will not compensate for the increased load "vs" lower air intake rate. You would be way under the 14.7 to 1 desired ratio

Yes, the system will be running rich at under those conditions. The MAP values are going to be at their highest level and high MAP means more fuel. We are also not running in closed loop fuel control. The engine is "lugging" throughout the entire range and it is not happy about it. If we were able to downshift like your car or truck does we could make the engine happy but we do not have that ability so we have to control the load on the engine by changing the prop size or lightening the boat.

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Nitrousbird

Most automotive engines go from closed loop to open loop at around 75% throttle. That's where the fuel maps come in more importance, as the O2 sensor is no longer being used as a reference, and the MAP and/or MAF sensors are being used as the only source of knowledge for the amount of air entering the engine. So the load is based on RPM vs TPS vs MAP sensor reading to determine how much fuel needs to be used.

Are we saying that the MAP sensor is not being referenced and the fuel injector cycles are based solely on the RPM vs TPS? Or are we saying that the fuel tables are not setup well enough for high load, low RPM situations (IE low RPM but high TPS and MAP readings).

It's all in the tune. I'm no expert (I've only done a bit of custom tuning myself - enough to be dangerous), but I have several aquitances and friends who are.

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edwin

The engine is "lugging" throughout the entire range and it is not happy about it. If we were able to downshift like your car or truck does we could make the engine happy but we do not have that ability so we have to control the load on the engine by changing the prop size or lightening the boat.

Exactly what I was thinking, similar to a manual transmission car starting out in 2nd gear, shifting to 3rd before it's spun up in 2nd, and so on.

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SmoothWaterMan

In a very simplistic way, it's like driving your 5 speed without gears 1-4. Find the car or truck that will do that, and the mfg that will stand behind it. You're already overworking the engine, so why make it worse? Don't you want your engine to run the best it possibly can? I'm all about optimum use and efficiency, and to do that in a boat means running within 200 rpm of the WOT spec, at WOT. It's not hard to achieve, but it's not going to come from the factory propped that way, unless you run the boat as it came, stock conditions.

Take the time to listen and place a little faith in what EngineNut has to say. I bet he has more marine experience in his pinky that most boat owners will ever see.

Peter

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Timmo

In a very simplistic way, it's like driving your 5 speed without gears 1-4. Find the car or truck that will do that, and the mfg that will stand behind it. You're already overworking the engine, so why make it worse? Don't you want your engine to run the best it possibly can? I'm all about optimum use and efficiency, and to do that in a boat means running within 200 rpm of the WOT spec, at WOT. It's not hard to achieve, but it's not going to come from the factory propped that way, unless you run the boat as it came, stock conditions.

Take the time to listen and place a little faith in what EngineNut has to say. I bet he has more marine experience in his pinky that most boat owners will ever see.

Peter

Thanks for your input, I've often read your contributions and consider the Crew to be a better and more rounded source of information when people from the industry such as yourself, Indmar and Bakes etc. contribute.

Although I own a Response that is used purely for skiing I have wondered what effect large amounts of ballast have on engine and transmission life when I read about, and see the amount of weight added to create the latest surfing wakes. Would never have thought about the WOT test. From what I can gather from your's and Larry's posts the comparisons between car and boat engine tuning/calibration are not always valid?

Edited by Timmo

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Big Jay D

Engine Nut,

You are on target until the next to last paragraph. As an experienced high performance engine tuner (not just hand held tuners but ground up stand alone system) I have a hard time believing that the ECM's in these boats are running a TPS vs RPM fuel map. I also have a hard time believing if it was a TPSvRPM fuel map that the pulse width would be set at a time where enough fuel would be squirted to wash the cylinders.

I could be dead wrong but if the ECM in these boats are that archaic is no wonder some many owners have some many issues with their boat engines. It's not a matter of lugging the engine it's a matter of having enough timing built into the curve to burn the fuel at a temperature and AFR that will not over heat the exhaust valves.

Maybe I just need to drop in a LS3 with a GM computer and a HP Tuners kit. Tune it and be done with the garbage that PCM, Indmar, all the other companies shove down our gullets.

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Lance B. Johnson

All THEORIES aside I think engine nut is grounded in reality. Let's face it, he's seen the damage first hand from the engines that get sent in for warranty. Washed cylinder walls and failed cats are reality.

That said, all you "engine guys" know it's not good to lug an engine.

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Lance B. Johnson

Actually my question for engine nut is, should I replace the damper plate in my 05 monsoon given that it we ride with a lot of weight? It's at 430 hours. It sure seems that the 05s are prone to failure. Has indmar looked into the root cause of these failures?

Edited by Ruffdog

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MalibuNation

Larry thanks!!

I just PMed you and what would make another good topic ... what about fuel additives? Seems like Indmar only recommends only marine Sta-Bil. What about other dry gas additives or fuel injector cleaner?

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SmoothWaterMan

From what I can gather from your's and Larry's posts the comparisons between car and boat engine tuning/calibration are not always valid?

Well, I'm not sure who has compared the auto world to the marine world, but they are vastly different. I have limited knowledge of the auto world, but here's a good rule of thumb that's easy to understand.

Comparing the job of a marine engine to an automotive engine is like hooking a loaded trailer to a car, finding an endless mountain to climb, and attempting to hold 70 mph all day.

This would be an attempt to simulate the constant load of a marine engine. Now, if you are propped incorrectly on your boat, shift the car up a gear and see if you can still hold 70 mph all day, for the life of ownership - 3-5-10 years?

The only time a marine engine is not under load is when you're not moving.

Peter :)

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'01 wakesetter vlx

With regard to the WOT test described above, how should one account for wedge? I would expect a significant impact on engine load, but I've always thought it we weren't to run the wedge deployed at WOT speeds... I have a manual wedge.

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shawndoggy

With regard to the WOT test described above, how should one account for wedge? I would expect a significant impact on engine load, but I've always thought it we weren't to run the wedge deployed at WOT speeds... I have a manual wedge.

I think he's saying add all the weight, drag, etc etc (which I'd think would include the wedge) and if you can't approach redline, you are overpropped.

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Ndawg12

With regard to the WOT test described above, how should one account for wedge? I would expect a significant impact on engine load, but I've always thought it we weren't to run the wedge deployed at WOT speeds... I have a manual wedge.

Borrow another thousands pounds and leave your wedge up, shouldn't go over like 30mph with the wedge down I've heard.

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jkendallmsce

NOt trying to go off on a tangent, but what about a 2 speed transmission??

I have not seen how it works, but MB uses a 2 speed trans on/in some of their boats.

Not sure if engineering wise is doable, but makes sence, vs having to change out props depending on what you are doing.

Edited by jkendallmsce

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shawndoggy

Borrow another thousands pounds and leave your wedge up, shouldn't go over like 30mph with the wedge down I've heard.

I think it'd be unlikely that you'd actually go that fast if you are heavily weighted. Rather, you'd be redlining at 25.

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shawndoggy

NOt trying to go off on a tangent, but what about a 2 speed transmission??

I have not seen how it works, but MB uses a 2 speed trans of some of their boats.

Not sure if engineering wise is doable, but makes sence, vs having to change out props depending on what you are doing.

2 speed tranny no longer offered.

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jkendallmsce

2 speed tranny no longer offered.

Do you know why?? bad design, poor engineering?

I had only read about it, but thought it sound like a great idea....way better than struggling with swapping out props...

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85 Barefoot

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

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jkendallmsce

I read about it a few years ago, tried contacting/finding more on the local MB website, but they never advertised much about how it works, etc.

You'd think, at least I have always thought, it would work like a champ. You could put the boat in 4 low to surf, etc, then back into high to get back to the ramp/dock??

Just like AWD in a lot of the cars and SUV these days.

More bells and whistles to play with and no mess or fuss to activate on or off....a winner for boaters who want it all!!!

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