Upgraded my motor from 305 to lightly modified 350 two years ago. Kept the Alpha with 1.65 gears. Was way underpropped @ 19p (6k rpm @ 53 GPS just for short testing) so the other day I installed a 23p mirage +. Really liked it at cruise and didn't have any problems getting on plane. After she was warmed up I hit a WOT run and got 4700 RPM @ 52 GPS. Then a clunk from the rear and brief drop in RPM. Backed off to idle, looked under the hood, and felt the drive. Everything seemed fine. Back to cruise, everything fine. Hit another WOT run and shortly after the same thing. This time there was also some clicking and ticking under the hood but hard to tell if it was from the motor or drive. I also noticed the gear oil level in the reservoir was higher than normal.

Limped back to the dock and it sounded kind of like a go cart and had a vibration in the rear. Oil pressure and temp were fine. A little harder to start (usually I just turn the key but i had to give it some throttle). Trim and/or steering didn't make a difference. Thought for sure I shredded the gears or busted a u joint.

So instead of running it on the muffs when I got home to try and isolate the noise/problem, I just started to tear it apart. U joints look and feel fine but I'll replace them anyway while it's off. I've forgotten more than a few times to lower the drive when tuning. Gears are like new, there's some fine metal stuck to the magnet but nothing large. No water in the outdrive oil or engine oil. No water in the bellows. No rust on the u joints. Alignment is good. The oil was dark coming out of the bottom but I haven't changed it in a while. It wasn't gritty and didn't smell burnt but it was almost black. It was like new coming out of the top.

Gimbal is rust free and greased. I'm not sure how it's supposed to spin but, if anything it seems tight. Doesn't grind but doesn't spin like a top either. If I spin the alignment tool it only spins about 1/2 to 3/4 turn. It didn't need it but I did change it out 2 years ago when I swapped motors. Can't recall for sure but I think I went cheap with a GLM because I was spending so much on the motor and other things at the time.

I didn't tear apart the lower unit but I'm assuming that's fine. The upper usually breaks before the lower, right? Prop shaft is straight and not cracked. Prop hub (flo torq) is not spun.

From what I read, you usually notice first signs of bad u joints and/or gimbal bearing when turning. My vibration and noise doesn't get any worse or better when steering or trimming. The vibration and noise is gone with the outdrive off. There is some light, irregular clicking in the motor but it was like that before this incident. I've adjusted the lash a couple of times but that didn't make it go away. Maybe the exhaust flapper? Not sure what it is but that's not my main concern right now.

Any ideas on what might be wrong and/or what to check?

Edit: I was just reading through the service manual and forgot to mention that one of the o rings on the drive shaft was broken. It was still in the groove but split. Could that be the problem? It was one of the two that ride against the gimbal so the other one should have been keeping it from grinding against it. Everything is still smoother on the shaft and gimbal.

I also checked for worn u joint shaft splines and/or engine coupler. No play at all there.

And that clicking noise is from the exhaust but not the flapper, probably leaking at the gasket. I'll re torque or replace the gasket. Probably just needs re torqued.

Is it supposed to sound like this and have so much play in the drive shaft? I've never take it off before but it always had a clunking sound if I would spin the prop by hand. If I pulled the prop back and spun it by hand it would spin without noise. Figured that was normal and when underway it pushed the prop back naturally. If I pull up on the drive shaft and spin it (two hands in the video) there is no grinding noise. But, with the drive shaft just resting naturally you can hear the grind. The impeller, housing and key are not on there. Is that what holds the driveshaft up a little? There also seems to be a lot of lateral play in the drive shaft but maybe the upper coupler takes away the lateral play?

Also, if I flip the drive and have the prop shaft vertical and the drive shaft horizontal and spin the prop shaft there is no grinding noise.

https://www.youtube.com/watch?v=r_zUGMXIP3M&feature=youtu.be

I'd go deeper into the gear set. When I junked my drive it made a clicking noise as you describe and then it finally let loose and made a metal milk shake...

Gears, bearings, cups, and splines all look good. I'm usually down for tearing anything apart but I don't want to disassemble any more of this lower if I don't have to.






Update on the oil... what was left in the lower case is dark green. Not new but not black either.

Did you use an alignment tool when replacing the engine?

Your issue may be in the drive coupler and not the drive.

Yeah, I used the tool and spun the engine 180 degrees to verify. Also installed a new gimbal bearing.

I thought it might be the alignment also. Maybe the mounts worked loose. That was the second thing I checked after the u joints. Also checked the drive shaft to coupler splines and absolutely no play there. There was no burning rubber smell or chunks of burnt rubber in the bilge so I don't think I spun the coupler. If I did spin the coupler I'd think the boat wouldn't move at all.

https://www.youtube.com/watch?v=1dDasBf1hbE&feature=youtu.be

Good news. Drive is fine.

Bad news. Tore apart a perfectly good drive and now I have to put it back together. LOL

Worse news. Low compression (30 psi) in 4 & 6 so I ether blew a head gasket or cracked the head. Haven't gotten it torn down that far yet.

3 & 8 are a little low. 160 and 165 respectfully. 3 went up to 170 with some oil in the cylinder. Everyone else is at 180 psi.

Could running that 23p mirage plus at WOT have blown the head gasket or was it just coincidence? Engine has never overheated. Doesn't even get above 180.

Would switching from 1.65 gears to 1.50 gears on the outdrive put less stress on the motor?

sounds like u detonated a piston or two., u loaded the motor down with the bigger prop and the fuel wasn't up to the task..

You nailed it. Guess I should cancel the Labor Day plans.

#4


#6


#8 also has some light scoring. That was the one that was at 165 psi. Guessing #3 has light scoring as well. Scoring is so light that I can't catch a nail on any of it. There is a little roughness at the top of the cylinder but it looks like it's above where the rings reach. I should be able to clean it off without a mechanical abrasive.

What do I need to do next? Is this light enough that I can hone and re ring 3, 4, 6, & 8 and a new piston for 6? Or do I need to get them all bored .040 over (already bored .030)?

New thread here since this is an engine issue now...

http://www.offshoreonly.com/forums/g...-now-what.html