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Gary Pelletier

New Engine - Hesitates/bogs when put in Gear

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Gary Pelletier

Hi Crew, need some help...

First some background: 2002 Response Barefooter with 350cu Hammerhead and 1700hrs. 3 weeks ago, engine started hydrolocking and discovered the aluminum heads had corroded allowing water into the cylinder. This isn't the first time - heads were replaced in 2011 for the same problem (boat has ONLY been run on a fresh water lake in Central Mass). Bad engine design in my opinion - aluminum heads on a cast iron block with open cooling is a bound to have problems!

Decided on a new motor given the hrs on the rotating assembly and past problems repairing the Hammerhead- did some research and discovered my options to reuse my existing accessories, fuel injection, ECM, etc were very limited. On advice, procured a GM Vortec 350cu Marine Long Block from Michigan Motorz - realized I was losing a few HP, but felt that was my best/lowest cost option to get back on the water quickly.

Motor was installed this past weekend- swap was straightforward.

New engine fired up fine and I set the timing to 10 degrees BTC at 1200rpm using the paper clip trick across pins 1/2.

Engine bogs down/stalls/backfires when put in gear (forward or reverse). If it doesn't stall, I can get it to run fairly decent - no issues through 2000rpm . Does seem to hesitate if I give it some strong throttle. Haven't had it up above 2000rpm yet - respecting the break in process.

Here's what has been done:

Fuel injectors were sent for professional cleaning during the engine swap.

Fuel pressure gauge installed - 45psi at key up, 40psi running....

New NGK TR5 plugs gapped at .045

Timing set at 10 degrees BTC using Clymer manual procedure (any other tricks to ensure timing set properly??)

New Cap and Rotor

New gas in the tank

New Fuel Filter and Fuel Pump Screen cleaned (June....)

Reminder - all swapped components ran great on the prior engine (3 weeks ago)

Any suggestions on what I should be looking at next?

Appreciate any advice Crew!

Regards -

Edited by Gary Pelletier

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JasonK

Does it rev smooth in neutral? Could it be a linkage problem?

Disconnect the shift linkage at the trans.

Shift into gear at the throttle like normal and see if it bogs. If it doesn't then its not the throttle linkage.

Then try this:

while throttle in neutral, shift the trans by hand at the trans mounted lever and see if it bogs. Then advance the throttle and see if it bogs.

If it's not related to linkage then I'd say it's a fuel issue. Start with a fuel pressure gauge.

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Gary Pelletier

JasonK - great suggestion, tried that but no joy. Same symptoms regardless if the tranny is being engaged. If I "double goose" the throttle, I seem to get beyond the hesitation and it runs "ok". Fuel pressure gauge is actually installed - 45psi at keyup, 40psi when running.

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MadMan

Have you checked for any DTCs with the shorting paper clip trick?

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Gary Pelletier

Not familiar with how to do that - anyone have quick instructions?

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jfw432

Sounds like an air leak or sensor issue to me. The sensor may still be good but could be a ground issue. Fairly easy to check by just unplugging the TPS and MAP sensors and checking for 5volts.

I just did the diagnostic trouble code thing on my own boat in hunt of a hesitation issue. http://www.themalibucrew.com/forums/index.php?/topic/56425-00-response-monsoon-engine-slow-out-of-the-hole/page-3

This is the link I got which gives you the codes and what they mean. I'd start with the code reading. LED lights are cheap and you'll have a paperclip laying around somewhere. http://www.pirate4x4.com/tech/billavista/MEFI/

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justgary

Wouldn't a 350 need a different MEFI program than a Hammerhead? The 350 is probably getting the wrong fuel and spark advance. Which MEFI module do you have?

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Gary Pelletier

justgary - this is the 2002 - 350cu in Hammerhead. MEFI 4 I believe. I wanted to upgrade to a Stroker keeping the same intake, fuel injection, etc, but my existing setup wouldn't handle the bigger motor without substantial upgrade (fuel regulator, fuel lines, ECM flash, etc). After much research, the GM Vortec Long Block was my only real choice for maximum reuse at minimum cost.

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Arick

How olds the coil? This may not be your issue, but it ended up being my issue. Not sure how you can check that its operating appropriately?

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Gary Pelletier

Arick - coil is original (13yrs). It worked fine on the prior engine - something to check..... Thanks -

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MadMan

justgary - this is the 2002 - 350cu in Hammerhead. MEFI 4 I believe. I wanted to upgrade to a Stroker keeping the same intake, fuel injection, etc, but my existing setup wouldn't handle the bigger motor without substantial upgrade (fuel regulator, fuel lines, ECM flash, etc). After much research, the GM Vortec Long Block was my only real choice for maximum reuse at minimum cost.

I did a similar change to mine. It was originally a 350 monsoon. I basically built a 383 monsoon. Kept everything except the stroke the same (heads, cam, MEFI 3 fuel injection). Thought I was going to have to work on the fuel mixture since the engine is about 10% bigger and has no feedback (no o2, no MAF). As it turned out, because GM/Indmar are very conservative with the fuel map (ludicrously rich), it was still too rich even with 383 cubes!!!

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Gary Pelletier

Madman - wow... I'm guessing I'm up against a similar issue.... Everything worked fine 3 weeks ago before the swap.

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MadMan

Madman - wow... I'm guessing I'm up against a similar issue.... Everything worked fine 3 weeks ago before the swap.

I don't believe your issue is caused by being overly rich, it just wastes fuel and horsepower. Drivability is ok when rich.

Built mine a couple years ago, leaned it out, running great. Because of the extra torque, I'm able to run the stock prop (14 x 18) with 2500 lbs ballast + passengers (2000 23 lsv).

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