Knock at Idle

[Tucker]

RE S200TXRW
Gents,
Have a stbd motor that has a audible knock at idle, sounds metallic. Just bought the boat and surveyor (Yam Tech) raised an eyebrow at the noise but didn't put it in the survey. Compression good with lowest 110 and highest 120. Paying the marina to rebuild 5 carbs and replace one. PO did not use any fuel additives and I got the ethenol nightmare. He also reported heavy carbon build up. I turned down that treatment because I can do that. What do you think the knock could be?

[Tucker]

Wrist Pin Test

RE 1998 S200TXRW 970 hrs
Gents,
Have a stbd motor that has a audible knock at idle, sounds metallic. Just bought the boat and surveyor (Yam Tech) raised an eyebrow at the noise but didn't put it in the survey. Compression good with lowest 110 and highest 120. Paying the marina to rebuild 5 carbs and replace one. PO did not use any fuel additives and I got the ethenol nightmare. He also reported heavy carbon build up. I turned down that treatment because I can do that. What do you think the knock could be?

Ok, Original titled as Knock at Idle, But I've learned a few more things. After the sea trial carbs leaked like crazy. Yam tech discovered slow speed jets tightened against seats and the needles bent. The replaced carb had the needle piece broken off and jammed in the seat. Paying marina about $2K for ultrasonic cleaning, 5-carb rebuilds, oiling linkage adjustment, and carb replacement. Also includes throwing the boat over and running to adjust linkage. Some say I'm getting screwed but real Yam techs all seem to be getting the big money up this way. PO admited to getting some hack mechanic to work on the engines. With some other dude screwing-up the motors, I'll at least have everything back to good condition.

I learned that a loose flywheel or stator could cause the same sound. Waiting for my new shop manual to arrive, but I believe I need to rent a flywheel puller and jig bar to remove the fly wheel. Also need to buy a torque wrench that goes up to 147 Lbs. The wrist pin check tutorial I read here seems to be easier but I need some clarification. Is the piston push check performed at a few degrees past TDC for each cyl? On the stbd engine, looking at the flywheel do I locate the hash mark at the 10:00 position or the 2:00 position?

[99yam40]

For 2K I believe you can buy all new carbs, so I would check the prices on line at this web site and buy them yourself or take it to a different shop.
I would not be spending that kind of money on a motor that has a knock until I knew what the problem was. You maybe throwing that money out the window if there is a major mechanical problem.

[Tucker]

OK, moving this to the top. Just took delivery of the boat Tues. Got an inch of snow and temp hasn't been above 28 deg, so nothing's going to happen soon. Question about wrist pin check test: When coming to TDC for each cyl. about how far past TDC do I advance the flywheel before applying pressure to the piston. Yamaha tech that surveyed motors and did the carb work still doesn't think it's a wrist pin.

[99yam40]

Sorry but I have not advice on your test but could it be a fuel pump problem? Seems I have read where some will have a nocking sound at idle if they are not full or sucking air, but may not happen on this motor.

[Tucker]

Thanks, fuel pumps are on my shopping list. It would be great if that was the problem.

[rodbolt17]

nope, fuel pump knock is STRICTLY 4 stroke.
its carbed so its NOT the O2 sensor draw tube.
I hope you did not pay much for it.

[rodbolt17]

and there are only 3 carbs on that model.

[Tucker]

What's the prognosis rodbolt? Is my wrist pin check procedure correct? It's on a neglected Grady that I did get a good deal on. If it ever get's above freezing I'll run it in the tank to get a good hear.

[Tucker]

It's got twins.