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57 GSi wonbt rev above 2200RPM

R

rowdyroady

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"I have a 2001 Chris Craft wit

"I have a 2001 Chris Craft with twin 5.7 GSi's with 270 hours on each. I just bought the boat, and it ran fine when I bought it (of course) but shortly thereafter it started getting sluggish at plane, losing power before finally just refusing to go over 2200 RPM or so. It runs rough and absolutely wants to shake itself off of its engine mounts anytime I try to throttle up. I changed the plugs, distributor cap, rotor and fuel filters. One fuel filter had some watery rust in it which I assumed was my problem at least for one engine...the other filter did not have any water in it. However, both engines display the same symptoms. The fuel pumps are fine, both high and low pressure are good. I have since added some Sea Foam to the one gas tank, and checked the gas filter several times...I seem to have gotten the moisture out.

I am at a complete loss on what to do next...this is extremely frustrating. Please help!"
 
"No EPM codes. I thought the

"No EPM codes. I thought the boat was entering Safe Mode as well...my first thought...but no ECM or whatever you call it codes stored whatsoever.

New gas...the boat started exhibiting these symptoms a few weeks after I got it...prior to a refill. New gas, full tanks, but the symptoms started before the gas fill."
 
Two separate tanks...80 gal ea

Two separate tanks...80 gal each for each engine. Strange both engines are exhibiting the same symtpms.
 
"A compression test won't

"A compression test won't hurt, but it seems odd to me that both engines would have at the same time valve or piston ring problems with just 270 running hours.

Dale, perhaps the seller knows something you don't? Perhaps the boat was stored for a long time and the gas has gummed-up the fuel system. Your engine seems to be TBI, in which case around each injector (part 7) there is a fine fuel filter (part 8). You should have 2 of those filters on each engine. Have you checked them?

http://www.volvopentastore.com/THROTTLE_BODY_INJECTION_SERVICE_KITS/dm/cart_id.9 63744532--session_id.643204790--store_id.366--view_id.312800"
 
Totally agree with El that thi

Totally agree with El that this would be weird to impact both engines with low hours. Certainly does sound likely to be a fuel related issue. But burned valves would also exhibit similar symptoms. Are the engines back firing? What did the old plugs look like?
 
"ALl sixteen plugs were dry...

"ALl sixteen plugs were dry...but very sooty and black. Oh, and it was the original plugs...never been changed. No backfiring. I am going to likely turn the local Penta authorized dealer loose on this problem as much as I hate to do that. I am at wits end, and running out of ideas. Also, don't have any experience with TBI..."
 
Looks like it was running rich

Looks like it was running rich and that would point to a TBI/ECM related problem in my opinion. Did you check the throttle valve operation and the throttle position sensor (TP)? Maybe it is sticking and restricting the air flow? I believe TBI has 2 injectors and their tips are located above the throttle valve. The injector timing is controlled by the ECM and various sensors that monitor engine conditions and places the ECM into different fuel modes. I wonder if your TP sensor is bad and keeping the ECM in the acceleration mode. That would provide extra fuel by increasing the injector pulse rate and definitely load the cylinders with fuel. The ECM code would be code 21 or 22. This can be checked with a DVOM.
 
"Dale,

As a disciple of EL,

"Dale,

As a disciple of EL, I am a big believer in the SELOC manuals. Everything you need to troubleshoot the problems is there."
 
"Li,

THanks for the input..

"Li,

THanks for the input...I just purchased the SELOC manual. Should have in a week. In the meantime I will check the TP sensor although I had my dealer check the ECM...no codes recorded."
 
"Dale,

I'm not 100% sur

"Dale,

I'm not 100% sure the TP will throw a code; SELOC isn't clear on that and I have seen cases where there wasn't a firm code and the TP was bad. You can use a DVOM to check, I will summarize directions in following posts."
 
"TP will send a signal voltage

"TP will send a signal voltage to ECM- 0.7v at idle to 4.0+v at wide open throttle. Beg, borrow or steal a code reader and connect it. With ignition off disconnect TP sensor, start engine and allow to idle for 2 minutes. Turn off ignition and retrieve any stored codes. If code 22 locate and repair any bad connections. If no codes replace the TP sensor. Next step to follow."
 
"With ignition off disconnect

"With ignition off disconnect TP sensor harness, turn on ignition but do not start engine. connect DVOM between A & B harness terminals. If reading over 4v you have a short to voltage in the circuit between J2-19 and the harness connector C. If everything looks okay then it is in the ECM and it has to be replaced. If the reading is under 4v you have an open ground between J2-18 and the harness connector B. If this checks out okay and the ECM connections are okay, replace the ECM."
 
"In my experience 99% of the t

"In my experience 99% of the time the TP sensor goes bad just like automotive applications. The throttle body gets gummed up, the shaft starts to bind and the TP gets thrown out of whack. All it is is a potentiometer that provides a variable signal to the ECM with the opening and closing of the throttle. Check it and clean as needed and also check the harness connectors going into the ECM. It is probably something simple."
 
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