Port 5.0 MPI losing power

[pete42003]

If I have missed a thread on this please forgive me. I feel as though my port motor has lost about 600 RPM's when WOT. Now this is only when my starboard motor is running at around 3900. I WOT the port and the highest it reaches is 4200. Vice versa, the starboard will push the boat to 4800 which is where i've noticed WOT to be. So in another words, my Starboard motor has more propulsion than the port. This will be a winter project to look at. The motor doesn't stall, or sputter. I will check for growth, prop damage when it comes out of the water later today. Any other ideas would be helpful! Thanks all...

[mmwjr]

Pete what rpm do you get if you push both engines to WOT? When the starboard is turning 4800 what is the port rpm?

Yes growth and prop damage are where to start. If these check out and since the engine is not showing a performance issue check the fuel pressure next to see if the engine is starving at high rpm.

[pete42003]

4800 is the WOT RPM's. When the starboard is running at 4800, the port will run at 4800. It is when I back off the starboard to about 4000 that the port motor will lose power. I didn't play with the throttles when I bought the boat and can't compare from earlier trials.

[mmwjr]

Ok so I have not owned twins so no expert.

First why would you run one engine at WOT and back the other down?
What happens if you leave the port engine at 4800 and back the starboard to 4000?

Seems the engine left at the higher rpm will get an increased load by backing down on the other engine and this load would cause it to drop rpms.

[pete42003]

I had noticed the Port RPM's were running a little low and was just testing. If I do that, the boat loses speed and the Port RPM's drop. Vice versa, the starboard motor will not lose speed and will not drop in RPM's. Im just wondering if this would be normal. Basically, the starboard motor feels and performs stronger than the Port.

[mmwjr]

Being MPI you could have a boat mechanic use a merc scanner to see if any bad engine codes exist.

[ertyqway]

Have you visually checked the outdrive trim to make sure both outdrives are even and level? Having one out drive higher than the other can create problems similar to what you describe.

[Kevlar7r]

I have a similar issue, my port motor is noticeably stronger than my starboard. Its also 10 years newer. I just work my throttles accordingly and keep the engines balanced.

[pete42003]

I have a buddy who has a scanner. I will have to get a hold of him when Spring arrives.

[pete42003]

I checked it when it was pulled out of the water a couple of weeks ago. I have some adjustments to do on the trims. Don't think that was the issue. But I was curious to see if anyone had similiar problems. Getting on plane isn't a problem.