Noise and vibration @ low RPM's

[ppidgursky]

Since the rebuild, the boat has been running pretty good...except I have noticed that at low RPM's the motor will vibrate and will be somewhat noisy. Once I get past 3000-3500 RPM's it clears up and runs great. Anyone have any idea? It runs good, just sounds unhealthy. Any sugestions are welcome.
Motor is a Yamaha 1989 50ELF.
History: Have had the block bored 20 over, new pistons, rings, fuel pump, carbs rebuilt, new fuel lines, rebuilt water pump, new batteries, new gaskets and orings all the way around.

 

[ppidgursky]

Re: Noise and vibration @ low RPM's

I could really use some help here fellas.
When I start the motor she will run ok for a second or two then the noise comes. Almost sounds like gears or something. The sound sounds the strongest on the left side, near the bottom of the motor. I removed the foot and checked the spines on the shaft...they are fine. I check the oil in the foot it was low, and milky so I changed it. Still happening. If the foot was leaking oil, where would it leak from?
When I rev it up some it clears up. Maybe 2-2500 rpms and up. This happens in and out of the water.
I rebuilt the motor, and she was fine at first. The rebuild went smooth I guess. Everything put back together ok and smoothly. What could be wrong.. or do I need to tare it down again?

 

[JUSTINTIME]

Re: Noise and vibration @ low RPM's

bring it back to the rebuilders

 

[ppidgursky]

Re: Noise and vibration @ low RPM's

I would, there is one catch. I did all the work. That is how I can say I thought it went smoothly.
Any ideas?

 

[JUSTINTIME]

Re: Noise and vibration @ low RPM's

u might not have the carbs tuned and timing right

 

[Ray Neudecker]

Re: Noise and vibration @ low RPM's

Did you rebuild the carbs? Link and sync? Reset idle timing?

 

[ppidgursky]

Re: Noise and vibration @ low RPM's

The carbs were rebuilt a few month back, and then torn apart and cleaned recently. I just bought a timing light and I am researching how to check the timing. I have the shop manual and I am reading all I can before I smart messing with.
My first thought was timing, like a misfire, but I am not sure.

 

[ppidgursky]

Re: Noise and vibration @ low RPM's

Hello Again,
I removed the foot and hooked hose directly up to the water tube. Noise was still present. I was able to tune the carbs in some and got it where it does not do it as often, but will come and go. Once it starts, it is usually enough to basically stop the motor. She will spit and sputter and sometimes quit. If I give it gas before she quits, I can save it and keep it running.
Question: When I had the foot off, and I shut the motor, and water off, I noticed white foamy liquid coming from the exhaust port. I smelt it, and it had no noticable oder like gas etc. I also checked the spark plugs, and looking down the hole I noticed the top of the piston was wet, also on the end of the plugs. Unburnt fuel/oil... I don't know?
Would that mean the head gasket?

 

[Ray Neudecker]

Re: Noise and vibration @ low RPM's

The water exits through the exhaust tuner and housing. Combined with the unburnt fuel will make a grey gooey mess. Everything so far says you need to get the carbs and timing right. A compression test will tell you if the head gasket is OK.