Inboard Mercruiser 74L EFI Only Goes to 3600 rpm

"This year my stbd engine only

"This year my stbd engine only reaches 3600 rpm at full throttle. The port engine runs normally at 4200 rpm. The stbd engine starts up fine and runs smoothly, and at normal temp. I changed the fuel/water filter but it didn't help. I switched fuel tank lines from the port engine to the stdb engine (thinking it might be the stbd tank anti-syphon valve) but still didn't help. Props are the same as least year and inspected ok last week in the water. I have engine synch control on the engines and the slave engine is the stbd but it hasn't been altered since last year)and works ok. Engine rpm is still low with the synch disengaged. Any suggestions will be greatly appreciated! Thanks."

"Ron,

I am experiencing the

"Ron,

I am experiencing the exact same situation with a pair of carbureted MerCruiser 454’s. The boat ran fine up until a few weeks ago when the starboard engine began only reaching 3000 rpm at full throttle. Because of the loss in power, the port engine will only reach about 3600, but it seems to still have its full power. Both engines run smooth and at normal temperature up until the point where the starboard engine loses power.

We’ve changed the water separators, bypassed the anti-siphon valve, given the starboard engine a full tune up, and even switched the carburetors from one engine to the other with no change in performance. This weekend we’re going to try a new fuel pump and supply hose from the tank.

Hopefully someone on this board has had a similar experience with such a mysterious power loss.

Dave"