V/P 5.7 GI-D not reaching above 3400 rpm

[KrisPbacon]

I have a 2003 fourwinns 328vista with twin V/P 5.7 gi-D model engines. My port engine will not go over about 3400 rpms under load. It will in nuetral. The scanner showed no codes. It has new plugs, csp, rotor and wires and fuel pump and filters. Compression test is 180 top and 155 bottom. vacuum test is a steady 14. Fuel pressure is 45psi at the rails. The engine idles a tad rough but nothing crazy and it accelerates smooth and steady up to 3400 but thats all it’s got if the other engine is WOT. If i back the starboard engine back to synch them up the port will drop to 3100 once its lost the help of the other. Any ideas?

 

[alldodge]

Compression test is 180 top and 155 bottom

Explain this a bit more please?
And what's the motor serial number?

 

[KrisPbacon]

4012093720 is the Serial no. DP-SM outdrives. 180 was my highest cylinder reading on the compression test and 150 was my lowest.

It was out of the water getting a gimbal bearing replaced and after about 20 hours, It started losing power sporadically but would immediately recover. The low pressure fuel pump plug had a burned contact. I replaced the plug and about a week later it started what it's doing now. Its sluggish and barely get's up to 3400 RPM and only if the other engine is WOT. I changed the fuel pump, and spark plugs. I has new wires and cap and rotor from a tuneup before spring. I ran a vacuum test and it was what it is supposed to be. Compression test, same thing. checked the timing, it was spot on. It's non adjustable anyway. Fuel pressure is 45 at idle and 45 under load. In nuetral it runs perfect, it's only under a load. One of the techs from the marina came with a code reader today but it wasn't throwing any codes. I'm at a loss. I'm wondering if something has come loose inside the outdrive that would cause it? Any advice would be appreciated.

 

[alldodge]

Thinking the motor might need a valve job with your compression numbers. A new motor would be 150 so with seeing 180 the gauge is probably off. If we reset the 180 to 150 which puts the 150 at 120. In any case there lowest should be no more then 10% from the highest

Before pulling heads it would be good to see a scanner connected to the motor underway. Then record the TPS and MAP readings under load. Want to see if the TPS is going to 100% and the MAP is providing full range

How many cylinders where in the 150?

 

[KrisPbacon]

I'm ashamed to admit it but it was just cap and rotor. When I did the tuneup at the start of the season, they sent the wrong cap and I completely forgot that I did plugs wires on both engines but cap and rotor on just one. I changed cap and rotor and it runs like a champ! Thanks for the response though.

 

[QBhoy]

Cap and rotor makes sense here. But just wondering about your 180 psi reading. Only explanation for that (given your lower results on others) would be a valve sticking or fuel or water in there perhaps.