engine knock

[1stevel]

first time boat owner here, i purchased a 1990 galaston 185 with a rebuilt motor its a 4.3 mercruiser and it seems to run ok but when i give it some gas around 3200 rpm i hear a knock that goes away, my question is from what i have read here in the forums is that it could be the exhaust flappers, is this normal or something to be concerned about? any help would be appreciated. thanks guys!

 

[Hansolo99]

Re: engine knock

So let me understand you hear a knock at 3200 RPM and then it goes away? After you pass 3200 RPM or after a while at that RPM??

 

[1stevel]

Re: engine knock

as soon as i hear it it starts to go away, its not constant and there is no noise at idle. i want to say it sounds like a rod Knock but it goes away.

 

[Hansolo99]

Re: engine knock

OK so if I understand if you keep it at 3200 RPM the sound will start but then go away?? You are not moving the throttle up or down once the noise is heard correct??

 

[1stevel]

Re: engine knock

that is correct!

 

[Hansolo99]

Re: engine knock

Have you checked you oil pressure when this is happening??

 

[1stevel]

Re: engine knock

30 to 40 psi