A scary noise Indeed

[Keepseln]

A noise that scared me,

I have a 1989 suntracker party barge with a 90hp 2 stroke Mariner engine (serial #b175157). I keep the boat in a slip on the lake.

Sunday, after the usual start up problem, we putted over to the fuel dock for gas. After fueling up and adding the oil to the gas. (injection system removed by previous owner) Fired the boat up and heard a noise that sounded like a car with a bad rod bearing. I mean CLANK CLANK CLANK CLANK CLANK CLANK CLANK

I immediately shut off the engine, and started looking for a tow back to my slip. Once in the slip I thought ?lets have a look,? started the motor again and it sounded like it has all year. Deciding to err on the side of caution we went home.

My question is about crank case oil, because if it were a 4stroke motor I would make sure the oil in the bottom end was in good shape.

Any thoughts please share.

Thanks
-JB

 

[sschefer]

Re: A scary noise Indeed

I'll take a wild guess at something that's easy to check for. How about water in the fuel.

 

[fishmen111]

Re: A scary noise Indeed

Could have just been a piece of carbon. If it sounded like a rod, I would check it to be safe. Pull your plugs and rotate the flywheel till a cylinder just starts the down stroke. Gently push the top of the piston with screwdriver or such and feel for downward movement without the flywheel moving. If you feel any movement, do not run it until you fix the rod/piston and the clogged carb that caused it. Check the compression while you are at it. If it cleared up on it's own, probably just a piece of carbon or piston slap due to a stuck ring that freed itself. If not the rod assembly, do a decarb.

 

[Keepseln]

Re: A scary noise Indeed

I?m going out to do the tests you?ve described, thank you.

This may seem like an odd questions (I know there are no stupid ones) but what about the crank case oil. Is there a way to check it, does it need to be changed like in a car? Also what should the compression be?

-JB

 

[fishmen111]

Re: A scary noise Indeed

You have a 2-stroke motor, therefore there is no crankcase oil. The rotating assembly lubrication comes from the 50:1 oil you mix with the gas. You are running a 50:1 ratio, correct? Your compression should be above 100 psi, but more important is the varience between the three cylinders. The readings should be within 10% of each other. example - 122, 115, 117=good / 122, 115, 90=trouble. Good luck.

 

[Keepseln]

Re: A scary noise Indeed

Thanks for the info
I'll let you know the outcome

-JB