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zcobrausa

Response Monsoon340 won't go above 3400rpm

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zcobrausa
Posted (edited)

I have a 2004 Malibu Response RLXI with a Monsoon 340.  Went to wake the boat up from hibernation today. Reconnected the hoses and put the drain plugs back in.  Put a new impeller in and started it up.  Once it got to temp I shut it down and changed the oil.  Restarted the motor.  Temp came up to maybe a touch above 160 after several minutes at idle.  Idle was just below 700 rpm.  Took the boat out and it had a pretty good vibration going through  1550 rpm and then smoothed out but had no power.  Temp stayed at 160 or little below when at speed.   I could get up to about 33 mph and around 3400 rpm but that was it.  Thoughts?  I only use non-ethanol gas and had stored it with Stabil.  Thanks in advance.

Edited by zcobrausa

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oldjeep

Cap/rotor /plugs would be the first and easiest things to check. 

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ORMailbuboater

Fuel filter or contaminated fuel.   Sounds like it might be starving for fuel.  Change the fuel filter.  Check the gas.  Good luck.  

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zcobrausa

I plan on doing the cap, rotor, plug wires.  However, I don't think that is it.  I just took it out again.  It definitely has a pretty good vibration around 1500 rpm then smooths out.  It definitely won't go past 3400 rpm when its in gear.  In neutral it seems to rev normally ( I went up to 4000 rpm).  Initially I thought I had a cylinder missing but it should miss in and out of gear.

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UWSkier

sounds like fuel delivery under load is issue, unless something is wrong with the running gear.  Can you turn the prop by hand when it's on the trailer?  Any funny noises from transmission?  You check trans fluid?

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tbullard

I went thru this last year and after much research it could be one of many things. What fixed mine was replacing the Ignition control module.

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oldjeep
16 minutes ago, zcobrausa said:

I plan on doing the cap, rotor, plug wires.  However, I don't think that is it.  I just took it out again.  It definitely has a pretty good vibration around 1500 rpm then smooths out.  It definitely won't go past 3400 rpm when its in gear.  In neutral it seems to rev normally ( I went up to 4000 rpm).  Initially I thought I had a cylinder missing but it should miss in and out of gear.

Vibration at a low rpm that goes away at a higher rpm does not sound like fuel. 

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zcobrausa

Not familiar with how the computer advances spark or if any sensors are in play. Previous boats had a mechanical advance.  Could that be the issue.

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UWSkier
2 hours ago, tbullard said:

I went thru this last year and after much research it could be one of many things. What fixed mine was replacing the Ignition control module.

Good call. Easy fix too

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Woodski

@zcobrausa:  Maybe you solved your issue already but if you have not:  Before you just start throwing parts at it, I suggest you think through every thing you did from shutting off the key the very last time before the problem to when this problem started.  That will make forum troubleshooting potentially much more accurate.  Good chance something you did will either be it, cause it or be a clue as to what the issue is.

The vibration could be several items, but if nothing has been disturbed from an alignment, the prop shaft did not get spun dry and the prop has not been dinged or installed incorrectly consider the following.   The most likely cause of a vibration tends to be an engine misfire, probably electrical (ie: bad plug, wire, rotor, cap, crossed plug wires) based on your comment that it smooths out at higher RPM.  An engine will run up to redline (5000 RPM+) out of gear easily with no load applied and you will be hard pressed to hear any miss w/o a load applied.  So, check the rotor and distributor cap, verify the correct firing order, check spark plugs for any cracked ones & look to see if they all have the same color and are not wet.

You can check your advance curve with a timing light, simply mark the crank pulley at 8 and 32 degrees BTDC, 8 for idle and 32 for max advance.

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zcobrausa

Replaced cap, rotor, wires and plugs.  All issues are resolved.  Plugs looked pretty good.  2 plugs had some light dry fouling relative to the others but weren’t terrible.  Cap didn’t look bad but one connector was not as shiny as the others and plug wire didn’t seem to snap on that one.  Also noticed post from the coil wasn’t shiny either.  I lightly sanded it back to being shiny.  I did check the MEFI with my test light and it was throwing code 81 which can be several things including an injector but since it’s running fine now I am not going to hunt anymore.  It’s possible I have a slightly leaky injector but I think it’s been about 4 years and 350 hrs since the plugs were replaced.

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