Engine won't run over 3000 rpm

[cabowabojo]

We have a 1999 Malibu Response with a 350 cu. in. Chevy EFI Blue Monsoon engine.

After storing regular (87 octane) ethanol gas for 5 months with 1/2 the recommended Stabil

I put 5 gals. of this stored gas and 15 gals. of fresh 87 oct. ethanol gas in the boat's tank.

Now I can pull a skiier for about ten minutes @ 3300rpm without any problem.

After this the engine won't go over 3000 rpm no matter how much throttle is added.

The engine will hesitate & sputter but stays @ 3000rpm.

After the first time it refused to run over 3000 rpm I added 8 ounces of Sea Foam, 3 ounces of Startron by Staybrite, and have replaced both fuel filters.

It still won't run over 3000rpm after 10 mins. of running at 3300.

Does anyone have any suggestions of what may be causing this?

-Tnx.

[tvano]

imho your ecm is forcing 'limp mode' (interrupts spark to half the cylinders).

i'd be looking at water temp sensor first.

there may be two water temp sending units on your rig; one for the gauge and another for the ecm.

i think the ecm's temp sensor provides a ground upon fault so temporarily disconnecting the wire to the sending unit may be worth a go.

i searched on 'limp mode' and found the following comment by 99response "limp mode can only be from oil pressure, engine temperature, and transmission temperature". i'm not sure that lack of oil pressure won't cause the mill to shut down completely.

[lonster]

My experience with limp mode was about 1800 rpm...3000 seems high

Edited July 26, 2012 by lonster

[tvano]

My experience with limp mode was about 1800 rpm...3000 seems high

you may be right, my reference shows about 2000 rpm.

if it's not limp mode then i'd head towards the ignition (distributor cap, rotor, etc.).

[jk13]

if it's not limp mode then i'd head towards the ignition (distributor cap, rotor, etc.).

I was going to ask when the cap , rotor, wires, and plugs had been done last. Sometimes they won't act up until the engine is fully warmed.

[SeanQ]

I was going to ask when the cap , rotor, wires, and plugs had been done last. Sometimes they won't act up until the engine is fully warmed.

That's my bet, I'd look at the cap/rotor and plugs next.

[Ndawg12]

Would the OP have a filter screen in his supply line?

[lonster]

prop damage? recent prop chnage?

[k2michelin]

Consider a fuel filter change as well -- symptoms sound similar to those exhibited by my 2003 Response with Monsoon 335...

[NorCaliBu]

How long have you owned the boat? Ever overheated it? Check your oil and make sure it's ok. The symptoms you describe could be a blown head gasket. If your oil looks like a chocolate milk shake, you've lost a head gasket. If the oil looks fine then start checking plugs, wires, cap, and rotor. Also check the coil. A coil shorting out will get extremely hot which then further impedes it's performance.

Good Luck. Keep us posted.

[RTS]

It is a very real possibility that your ECM is limiting your RPMS to 3000. I would swap out your engine temp sensor right away. Its a cheap and easy DIY project. Per Indmar, your Monsoon has a phased warm up procedure, that limits RPMS until engine comes up to temp.

<103 degress - 3000 RPM

104-139 degrees + 10 seconds - 4200 RPM

140 degrees + 10 seconds - Full RPM

That fact that you are stuck at 3000 RPM tells me it is very likely that your ECM thinks the engine temp is less than 103 degrees.

Edited July 30, 2012 by RTS

[NorCaliBu]

That fact that you are stuck at 3000 RPM tells me it is very likely that your ECM thinks the engine temp is less than 103 degrees.

Good call.

[jwl019]

Also check the coil. A coil shorting out will get extremely hot which then further impedes it's performance.

Good Luck. Keep us posted.

Where is this coil usually located on the motor so I can check mine? 99 VLX w/ monsoon 325

[NorCaliBu]

Where is this coil usually located on the motor so I can check mine? 99 VLX w/ monsoon 325

Just follow the wire from the center of the distributor cap, it will lead you straight to the coil.

[cabowabojo]

after changing the original 13 yrs old distr. cap, rotor and ignition coil it ran great until I ranout of gas and put 10 gals of the old gas in thinkin it would work fine since the cap, rotor and ignition module were changed.

no such luck.

have now added 10 gals of fresh gas, will change out the 2 gas filters and try again this weekend.

[Nitrousbird]

Why do you insist on putting old gas into the boat?

[cabowabojo]

Why do you insist on putting old gas into the boat?

Good question that's the 1st response I expected.

sat. the gauge said 1/8 full. Had 2 guys ready to ski the course sunday am & off the lift it said empty.

rationalized that the previous problem was the old cap & rotor and ignition module and not the gas.

put 10 gals. of 6 mos. old gas in and after about 20 mins. of skiing.I was @ 2800rpm in limp mode.

finally ran out of gas and cleaned the gas tank dry thru the inspection float port.

works fine now. May change the gas filters and eventually spark plugs and wires end of ski-year.

Edited September 27, 2012 by cabowabojo

[wakeparadise]

Did you ever source the problem for this one? I have the same problem on the '11 VLX