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Dale974

New high output motor, can't get the performance i was told

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Dale974

This spring my 320 monsoon came apart on me and i opted to go with a higher performance 6.2L marine remanufactured engine to replace it.  It was a bolt in replacement so the 6.2 isn't a LS type 6.2 but i believe what they would call a 383 stroker type.   I was told this should get me 350hp and 425 ft/lb torque vs the 320 monsoon that's around 350-365 torque...   My hope was that i could stay with the same prop or maybe even pitch up one or two to be able to pull footers at 40-42 range without being completely wide open.   What i'm running in to is an issue to get to my full WOT level.   I used to run 4800 rpm on the old engine with 13x12.5 prop.   I am actually running a 13x11.5 now and stuck at 4700 rpm, which doesn't make sense to me if i have more torque, why do i need to lower the pitch to get it.  Just trying to figure out what might be keeping me from reaching that 4900-5000 wot?   the computer was reflashed for the new engine, and in neutral i can run it up to 5150 where it bounces around at the rev limiter...      new cap, rotor, wires, plugs, both fuel filters, still not getting there.   Fuel pressure at key up, and at wot is within specs for the 320.   Seems like the last quarter of the throttle makes a lot of extra noise, but only about 200 rpm if that....   possible my timing isn't advancing far enough?  etc?    just wondering if anyone had anything like this that might know what would be holding me back.   Compressions are 120-150 psi running at idle...  not sure i've totally done that check quite right, but seems like if it was compression, i wouldn't be able to run as strong...   I've put just over 200 hours on the boat boarding, skiing, etc so it should definitely be broke in...   any thoughts?  Thanks

 

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Woodski

@Dale974:  Can you add some more info, specifically some additional engine specifications:  camshaft, more specifics on the ECU flash & how it was flashed to match the new engine.  Assuming the camshaft is appropriate, and the GM marine small block uses a specific marine cam, the ECU flash may not match the engine configuration.  Was the engine correctly aligned & does the prop shaft rotate freely, is the new prop in good condition?  Compression test is basically a static test, not typically done with a running engine so intrigued with your process although I would assume that as a new engine compression would be fine.

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MadMan

If all else is equal (cam, heads, intake, exhaust) the 6.2 will make about the same horsepower as the 5.7, it will just produce it at a lower rpm with more torque.  Since it's ~10% bigger, it will make about 10% more torque and max HP will be at about 10% less rpm.

What happens when you run the 13x12.5 prop?

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Sixball

Same injectors?  Can they flow enough for your new demand?  I hope the noise is nor lean detonation!

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Dale974
On 10/31/2016 at 5:18 PM, MadMan said:

If all else is equal (cam, heads, intake, exhaust) the 6.2 will make about the same horsepower as the 5.7, it will just produce it at a lower rpm with more torque.  Since it's ~10% bigger, it will make about 10% more torque and max HP will be at about 10% less rpm.

What happens when you run the 13x12.5 prop?

the 13x12.5 runs around 40 mph empty at 4400 rpms

13x12 - 40 at 4700

13x11.5  - 40 at 4750

 

On 10/31/2016 at 8:22 PM, Sixball said:

Same injectors?  Can they flow enough for your new demand?  I hope the noise is nor lean detonation!

well i had debated if i could be short on fuel, my pressures seem good, but i'm not sure how the computer is flashed so i don't know what its calling for.

 

On 10/31/2016 at 5:03 PM, Woodski said:

@Dale974:  Can you add some more info, specifically some additional engine specifications:  camshaft, more specifics on the ECU flash & how it was flashed to match the new engine.  Assuming the camshaft is appropriate, and the GM marine small block uses a specific marine cam, the ECU flash may not match the engine configuration.  Was the engine correctly aligned & does the prop shaft rotate freely, is the new prop in good condition?  Compression test is basically a static test, not typically done with a running engine so intrigued with your process although I would assume that as a new engine compression would be fine.

specs i was given on the cam to give to the guy flashing the computer were as follows:

Cam Lift: .431/intake, .451 exhaust

Duration (@.050 in): 196 intake, 206 exhaust

 

that's about all he had to go on, so i kinda wonder whether my computer would be flashed very aggressive at all to actually give me the rated power...

i never messed with the engine mounts, but when we put the new one in, the flange on the trans and the flange on the shaft were measuring true, when i change props, as soon as the locking part of the nut comes in to play i have to hold the prop or the whole thing will turn easy.

 

I called the engine place again today, hopefully i'll hear back from them soon.  they were supposed to call me as soon as they came in from the shop, but they were also going to do that two weeks ago, so i guess they must never leave the shop, ever!  :(

 

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Woodski

@Dale974:  Those specs imply standard GM Marine cam and same one from previous engine.  Are all the props same brand?  Do they all have same cup also?  It is good the shaft turns free, generally when an engine swap or even R&R is done, a shaft alignment is performed to ensure correct engine position relative to shaft. Might be a process you want to run through, several threads cover the process on this site.

Your airflow at higher RPM will pretty much document the high end power availability thus available power with either engine combination will be close, you should see a larger effect on acceleration due to more torque and also, check for any prop slip.

You might also want to run a speed v. rpm plot with additional speeds to see prop slip.  Speeds to include would be 10, 20, 30, 35 mph or something similar so you can plot out the curve and see the differences in props.

 

Edited by Woodski

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boardjnky4

The increased torque has really no affect at that RPM (4,000+). You need to do some reading on Torque vs Horsepower. Or work vs power...

http://www.hotrod.com/articles/hrdp-0401-torque-horsepower-guide/

At the end of the day, you need more horsepower, not Torque.

Edited by boardjnky4

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GaryB

Something is amiss, the new motor is making enough power to push the boat 40mph, period. It doesn't care which prop is on it.  Have you pulled plugs to look for lean condition or detonation? Stock heads? Or upgraded to take advantage of the added stroke? Have you checked the initial and total timing advance? 

My 97 Sunsetter lx (monsoon 320) will spin the stock CVP 13x13 stainless prop 5000+ Rpms to 46 mph. I replaced it with a 13x12 acme, it will pull 5100 rpm to 45 mph, I lost 1 mph on the top end although holeshot , responsiveness, speed holding, are all greatly improved. I suspect it would spin the 13x12.625 acme. 

Edited by GaryB

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Dale974
5 hours ago, GaryB said:

Something is amiss, the new motor is making enough power to push the boat 40mph, period. It doesn't care which prop is on it.  Have you pulled plugs to look for lean condition or detonation? Stock heads? Or upgraded to take advantage of the added stroke? Have you checked the initial and total timing advance? 

My 97 Sunsetter lx (monsoon 320) will spin the stock CVP 13x13 stainless prop 5000+ Rpms to 46 mph. I replaced it with a 13x12 acme, it will pull 5100 rpm to 45 mph, I lost 1 mph on the top end although holeshot , responsiveness, speed holding, are all greatly improved. I suspect it would spin the 13x12.625 acme. 

That is what i had suspected as well that if my 320 with less torque would push the boat 41-42, then the increase in power and torque should result in better performance and not having to run at the absolute max for barefooting when needed.    When we did compression tests, all the plugs looked good.  What is the best way to tell if i'm actually too lean.    I assume they are standard heads because supposively its a standard cam as well.  Initial timing is accurate at 10 degrees, i haven't checked timing above 3500 rpm or so, but at times i wonder if i was getting enough timing advance or not?  Still trying to get back with the engine guys, i haven't pulled the engine appart at all due to the warranty, but i'm always going to get a call back in a hour or so.  Still waiting for that hour to be up... 

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MadMan

It sounds like you and I have the same engine, stock monsoon 5.7 with a stroker crank to bring it up to 6.2.  Mine will spin well past 5k with a 14x18 prop (1.5:1 gear ratio) @45mph.   Timing wise, my MEFI 3 engine controller only adds 20 degrees advance when under load, so I have my initial set to 15 instead of the specified 10 degrees.

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Steve B.

Do you just rotate the distributor to advance the timing?

Steve B.

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MadMan
1 hour ago, Steve B. said:

Do you just rotate the distributor to advance the timing?

Steve B.

Yes, with the guidance of a timing light.

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Woodski

@Dale974:  I didn't notice but are you running a 3 or 4 blade prop?  4 blade props can 'hit a wall' where they can't push the boat any faster.  Sounds like other issues are more probable, but thought I would throw that in, my experience with older 4 blade props, the wall is closer to high 40's not 40 even.  Full timing advance is important, should be 32-34 DBTC for a SBC.  You can do an internet search and find timing maps (Mercruiser as one example) for the SBC which will be at least a good general guide on what the advance curve should look like.

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Dale974

@Woodski: the 12.5 prop is a 4 blade, however the 13x13 as well as the current 13x11.5 are both 3 blades.  After talking with the acme guy, i will probably stick with 3 blades because of the performance as well as the limits of the 4 blades on top end which i was not aware of. 

That being said i did hear back from the company with a few suggestions:

Hi Brian,

There are three things that we recommend checking with the reman 383 that you’re having problems getting full RPM’s out of.

 

1.       Make sure that after break in the valves have been adjusted. We recommend adjusting them to a “zero-gap” meaning when tightening down the rocker arm, tighten until the ticking stops. Do not turn any more after the ticking stops.

2.       Make sure that the engine is timed properly. Mistimed engines will not increase to the full RPM range.

3.       If the above two recommendations have been tested or done already, try changing the prop to a different pitch prop. This can need to be done if the replacement engine is a repower from a 305 or a 350.

 

Unfortunately i got this email the day after i finally winterized the boat.  I did check my timing and it ranged from 10 - 34 degrees which it reached at 3000 rpm.    When winterizing i did check the timing by putting it in service mode with a jumper wire to override the computer.  When doing that it seemed that the engine was actually at 8 degrees vs. 10.   When i initially timed the engine i did not realize i should override the computer, so i re-timed it to 10 degrees.  I'm wondering if this would have limited the advance that maybe i could have gotten slightly higher, although i thought maybe 34 could be about the max anyway. 

It does seem at times like there may be i slight tick sound, so i could possibly have a valve or two out of adjustment i'm guessing, so i'm hoping these help.  I just wish i would have known this before winterizing, but i couldn't wait any longer here in NW ohio.

As far as the prop goes, am i not thinking right that increasing my horsepower as well as my ft/lb of torque that i should be staying the same or pitching up, not down.  I always thought you'd pitch down to gain torque, so having the extra torque, i shouldn't need to repitch?

Anyway, that's what i found out for now and we'll see how that works.  Hope that helps you too @powbmps

 

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MadMan

Some thoughts:

I wouldn't adjust the valves to "zero gap".  There was an old hot rod trick back in the '60s and '70 where you would only turn the adjusting nut 1/4 or 1/2 turn after zero-lash instead of the factory recommended 1 turn.  This was to prevent the hydraulic lifters from "pumping up" because the valve springs were incapable of controlling the valves motion at 7000 rpm.  This doesn't really apply to the rpm you are using, with the factory recommended rpm range, the factory recommended lifter preload is fine.

Timing wise, a couple degrees won't make a huge difference.  By the way, when you measure the timing advance in the driveway, without loading the engine with the prop in the water, you are measuring the cruise advance, not the wide open throttle advance.  the wide open advance will be less.

If your engine produces more torque, it should be able to use a prop with a higher pitch (13 instead of 12).

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Dale974

good to know...  so you're saying not to make the valves quite as tight?

when i checked the timing we were actually running the boat down the river to check the timing advance.   when i re-timed it at winterizing that was on a fake-a-lake at idle...  

i would agree on the increased torque being able to pitch up, not having to pitch down...

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MadMan
25 minutes ago, Dale974 said:

good to know...  so you're saying not to make the valves quite as tight?

when i checked the timing we were actually running the boat down the river to check the timing advance.   when i re-timed it at winterizing that was on a fake-a-lake at idle...  

i would agree on the increased torque being able to pitch up, not having to pitch down...

Adjusting the valves with a hydraulic cam is kind of a misnomer. you're actually adjusting the lifter preload so it can do it's job.  The lifter automatically adjusts for thermal expansion and wear of the valve train, valves, rockers, pushrods, lifters and cam.  The 1 turn tighter after all clearance is removed is to put the lifter in the center of its adjustment range, so it can compensate for expansion and wear.

If the timing was at 34 degrees, at 3000 rpm, at full throttle, it's certainly not causing your issue.

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