Engine Noise

[chialord]

I recently replaced my MR140 with a rebuilt engine. Most of the top end items were used. I launched the boat and it idles great. Sounds great up to about 2400 rpm. After that the engine gets real "throaty" sounding and louder. Power is still good, but it sounds like there might be pre-ignition occuring. Compression checked out OK. I have no exhaust leaks. Adjusting timing did very little. I have good oil pressure and operating temperatures.<br /><br />I'm planning on doing a tune-up, but I was wondering if I had a centrifugal advance problem. Could this be an interal issue?

 

[Dunaruna]

Re: Engine Noise

Hi Chialord, welcome to i-boats!!<br /><br />What's an 'MR140'? Is it a v8?<br /><br />V8's will get throaty when the secondaries open, it's normal.<br /><br />Aldo

 

[chialord]

Re: Engine Noise

The MR140 is 4 cylinder. The old engine wasn't throaty and I'm concerned I might be experiencing some sort of pre-ingintion. I don't want to damage the engine.

 

[waterone1@aol.com]

Re: Engine Noise

The only way I can think of verifying the timing and advance curve would be with an advance timing light.

 

[waterone1@aol.com]

Re: Engine Noise

Your description of throaty, kind of leaves a-lot to the imagination. When you replaced the engine, did you make sure (with an alignment tool) that the engine and drive were properly aligned ? Did you check the gimbal bearing to make sure that it was smooth, well greased and not binding ? I'm just thinking that the "noise" may not be the engine itself.

 

[sea wolf]

Re: Engine Noise

My Cobra sounded like u described. Turned out to be the gimbal bearing. It would get louder & I increased speed. Grease the hell out of it & see if it quiets down.

 

[tee-boy]

Re: Engine Noise

I agree.