Carver 356 RPM issues

[cpoint]

I am sure I have another posting tagged on to some one else here somewhere. But this is a fresh issue, so here it goes. Last 2 weeks I noticed the starboard engine RPM is a bit on high side now. Been dealing with port side issues, hate to start on starboard side. Basically when starts RPM is at about 1000 RPM, where as port side is about 800 RPM. Before they used to be same. I don't hear anything funny from the engines. I know port side still has fuel issues, I am dealing with that. But starboard side RPM goes up slight touch on the throttle. So when both engines are, let say, 2500 RPM, the throttle lever on port is considerable amount higher than starboard side. So this weekend I decided to floor it, and pushed it all the way on both, I did get 20+ knots, which good. Port side stopped going past about 3200 RPM but was stable and steady. Starboard side went out to 5000 RPM. The sync gauge was somewhat centered. I did not hear wild sounds from either engine. So what could this be? After I went down to about 2500 RPM, though throttle levers for both engines were equal and when I went neutral both engines were at about 800 maybe 900 RPM. So could it be gauge? or because I did not use it so much needs to clear out by maxing the engines every so often? Would fuel issue cause it? on port side fuel issues cause RPM gauge to go up and down. The starboard side has no weird movements, just looks like high RPM last 2 weeks or so.

[mjk1040]

My first thought would be that if you have throttle body fuel injection system, clean your air sensor in the throttle body. Carb cleaner and a tooth brush. If this is dirty it will set your idle up because not enough air is getting to the sensor thus increasing your idle rpm. Sea Foam in your fuel tank may help clean internal system units.

[km1125]

Source of the post
Port side stopped going past about 3200 RPM but was stable and steady. Starboard side went out to 5000 RPM. The sync gauge was somewhat centered.

Something sounds really wrong there.

You should be able to noticably tell if the engines were at similar RPM or if one was around 3200 and the other 5000. If they both sounded the same (around 5000), then I'd say you have a port side tach issue.

[tomschauer]

something is strange here. If the starboard engine was "pulling the load" it would not get near 5000 rpm. It may just be a tach issue?
I believe I would pull out of the marina, and run on one engine at a time, feel how it pulls and listen for rpms while watching the gauges. You MAY find the port engine is doing all the work and the starboard engine is "freewheeling", either due to a sheared prop key or a slipping tranny. That would explain your low rpm port engine.
Just an idea.

[Viper]

Agree with ast couple of posts.
BTW, what is rated WOT for your engines? Can't recall what you have but 5K seems high. The best way to check actual rpm is to get a computer reading with a diagnostic tool, use a laser rpm reader, or a timing light with rpm feature. Then you can compare to what your gauges are reading.

Source of the post..... or because I did not use it so much needs to clear out by maxing the engines every so often?...

No

[tomschauer]

Yes, 5k seems high, that why I think there may be some slip somewhere????

[cpoint]

yes 5k is high, as I said this happened in the last week or two. I know port side has issues, so I know port side is not accurate due to fuel issues. Unfortunately I am not very good mechanically, simple things I can deal with. Anything bigger I need to take it up to a mechanic, so I am trying to get your feedback, so that I would have somewhat of an idea what kind a things may be an issue. I'll try to cleanup as suggested by mjk first, than if not solved, fork over some more money to my favorite mechanic I will try it out this weekend and get better sense of whats going on and post back here afterwords. Thanks to all for replying back.

[cpoint]

I will try with single engine to see how it goes (port, than starboard). I will also confirm, that when the 3k/5k was happening, it was not pulling on either side, it was going straight, but soon as slowed down either, than I had to compensate the rudder appropriately. That's why I am thinking they were both equal, and possible tach gauge may be going bad on starboard, maybe... Also, would seafoam cause any problems, would it be ok to added and if it helps great, if nothing, that's fine. But no bad side effects?

[Viper]

Try this; on the back of your tachs is a small cylinder selector switch in a little hole. There are numbers stamped around the hole. Note the position the switch is pointing to and remember that. Using a small standard/flat screwdriver, turn the switch back and forth several times. You may have to push the switch in before it will turn so don't force anything. Return the switch back to the original position then go for a ride, don't throttle up that high at your dock.

As always, do only one thing at a time then test before you do anything else otherwise you won't know which corrective measure solved your problem.

[bud37]

Agree with trying the above, I have had much the same and was corrected by working the selector switch around a bit.I guess the tell might be the sync gage was " somewhat centered", it gets signals from both the engines.....if it is good, then if one engine was at 5K rpm and the other at 3K rpm it would not be centered at all........good luck , hope it works for you.