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GM Marine engines - HP/Torq Curves included


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I was doing some research today and came across this web site. It has the information to all of the GM Marine engines, complete with HP and Torque curves. I found it interesting, so thought I would share if this is a duplicate, I apologize.

www.gmpowertrain.com/MarineEnginesControllers/Introduction.aspx

The interesting thing to me is the torque curves from engine to engine. The 350 produces MORE torque than the 409 upto about 2500 RPM, this could explain why some folks are so happy with the 350, also the 409 produces a similar amount of torque as the LS3 up until around 3300 RPM, then the LS3 has a power bump. The LSA is an absolute Beast producing massive power from idle. I put all 4 torque/HP curves on one sheet just for easy comparison.

The reason I was looking for this is I am planning to change props, to lower my RPM. I wanted to see how much less power the engine is producing at the lower RPM, to see if I would still have the grunt to spin the prop. The 350 starts bleeding torque after ~3200, the LS3 has a steady climb to 4600, so the different engines have VERY different power bands.

GM torque curves.pdf

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Indmar is very reluctant to hand out power curves for their engines....have had to press them (Larry and JT) to get their curves for hh and ls3 engines. ANd always wondering how accurate and under what pristine conditions to achieve those numbers! ha ha

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Doof,

It is my suspicion that it would be same "lies" for these. I.e. same dyno, same 93 octane, same pure o2 fed chamber, LOL...

So comparison should be valid, with the realization that there is still some real world fudge factor missing.

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The axis 450 is a souped up 6.0 so its anyones guess. Id say a little less dramatic torque curve compared to the ls3 though. Basically move the torque curve of the 6.0 up 25 ft-lbs across the board.

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Indmar is amazingly good at squeezing out every last HP that GM failed to squeeze out......and maybe some final adjustments when Indmar dyno's them! Like Darkside said!

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So according to GM, my 350 horse Monsoon makes 292hp.

assumption would be the 292hp motor is the one they actually use to make the monsoon, same cam, intake, tune and exhaust gm used. I highly doubt although lots of debate that the monsoon is the same motor internals and addons.
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dont forget a boat engine is running WOT often compared to a car which is running typically less than 3k rpms

boat is under much higher rpm/loads for much longer periods than a car so i assumed they had "safer" tunes but i could be wrong.

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I was doing some research today and came across this web site. It has the information to all of the GM Marine engines, complete with HP and Torque curves. I found it interesting, so thought I would share if this is a duplicate, I apologize.

Darkside do you have that data in excel where we could overlay them on the same graph and color code em?

then we need to overlay the lingenfelter pulley upgrade chart! haha

Edited by The Hulk
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much easier to propel a vehicle thru air, than a boat thru water.....ie why a bass boat with a 250 hp engine can propel the bass to 80 ish, while a 500 hp ski boat will only get to 40-45 mph. The wetted surface for the bass boat is much less than the ski boat.

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assumption would be the 292hp motor is the one they actually use to make the monsoon, same cam, intake, tune and exhaust gm used. I highly doubt although lots of debate that the monsoon is the same motor internals and addons.

I've said previously I don't believe the figures the marine industry uses. This architecture, with aluminum heads and a properly tuned intake manifold, made 285 horsepower in the Camaro, and I think maybe 300 in the Corvette. Both of those things would reduce power output, not increase it. With iron heads, the engine made 245 horsepower. 20% is ENORMOUS (and now we're over 30% given the iron heads). Gratned, the induction and exhaust systems would help in the marine application, but even gross numbers are not going to be 20% higher.

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