KNOCK KNOCK ?

[Larrys78]

I noticed a slight knocking sound comming from my Starboard engine starts at 1500 rpm and goes away at 2500 rpm 93 Crusader 270 TBI FI any sugestions?
only 350 hrs

[Redfin]

Hey Larry,

I'm assuming this is when you're in gear? Oil is topped off and tranny fluid? When was the last time you replaced the stringers & mounts under the engines?

[Larrys78]

Mounts, Engines and Tranies all were just replaced only 50 hours on them.

[prowlersfish]

Is the noise the same in gear and out of gear ?

[Larrys78]

Have not perfomed that test yet I will this week end

[mikeandanne]

Larry,see if you can isolate the sound if you can to get a better idea of where to look---- get a two or three foot piece of wooden mop handle or better yet the same length of 1/2 " plastic pipe--- with this you can listen to different areas of the engine ,just touch the areas and listen to the other end,make a fist around the end so you put your ear against the open part of your hand--- that way is a little safer--- run the motor up to the rpm the noise is at and have at it,you will not believe what you can hear like this--- hope some of this makes sense,I have done this for years--- try along valve covers first then work around the block and pumps etc--- Mike

[Lawman]

Knock or Tick. Mine had a ticking sound and I thought it was lifters, it turned out it was the fuel pump arm with a lot of play.?

[Larrys78]

Well after some investigation I'm still not sure what is causing the knock. It only is present when the boat is in gear and over 1500 RPM and seems to quite down at 3000 RPM. I took a stick and tried to isolated the noise and it seems to be the loudest when placed on the shaft log or layed against the shaft. The engine had no excessive noise, the tranie has slight knock but I think it is picking it up from the shaft. Tonight I'm going to take a look with my underwater camera just to make sure I didn't slip a zinc or some stupid is going on underneath.

[Larrys78]

Well after some investigation I'm still not sure what is causing the knock. It only is present when the boat is in gear and over 1500 RPM and seems to quite down at 3000 RPM. I took a stick and tried to isolated the noise and it seems to be the loudest when placed on the shaft log or layed against the shaft. The engine had no excessive noise, the tranie has slight knock but I think it is picking it up from the shaft. Tonight I'm going to take a look with my underwater camera just to make sure I didn't slip a zinc or some stupid is going on underneath.