1999 150 hp Mercury outboard bad rod bearing?

[bbigelow0763]

I have a 1999 Mercury 150hp 2-stroke EFI motor. Last week I started to get a continuous beeping alarm from the dashboard and immediately shut down the engine assuming it was the low oil alarm. I filled the remote oil tank and went to the lake for a test drive. The alarm started back up as soon as I put it in gear. It would also keep beeping (30 -40 times in a row) even in neutral. I removed the cowl to see if the oil feed tank was full. It was approximately 3/4 full and the beeping would stop if I raised the float. based on an online recommendation, I removed the oil tank cap and ran it at idle to refill but after a few minutes, it was still at the same level. At that point I put it back on the trailer and took it to the local marine shop. They were able to get the oil flowing but told me they hear knocking and that the power head needs to be replaced. I brought it home and removed the spark plugs to see if there was any play on the pistons and everything feels tight.

Question: is there an easy diagnostic I can do to determine if the rod bearings are bad/bent? The shop is saying it will be $6,500 for the replacement but I wanted to make sure that's the problem first. Any thoughts?

 

[bbigelow0763]

OK, I removed the heads to take a peak at the pistons and cylinder heads and everything looks fine. Just some carbon buildup in the top of the piston. No marks on the top of the pistons and the cylinders walls look like they've just been crosshatched Also, there doesn't seem to be any play in the movement of the pistons. If the mechanics were hearing knocking and its from the rod bearings, wouldn't there be contact marks?

 

[Dukedog]

bad rod bearing usually lets ya know pretty quick... may not be detectable with jus head removed.. can YOU hear any strange to you noises?..

 

[bbigelow0763]

When I spin the flywheel, everything sounds smooth. I can't detect any play in the rod bearings.