1993 Merc alpha one vibration

[ponchoman]

History- last fall I hit an underwater rock shelf and took out my prop. Since then I've noticed some vibrations at idle speeds, which would even out at cruising speeds. This spring I noticed some water in my lower units' oil, but not a lot.

First run if the year, had it wound out pretty good on the river trimmed up nice. All of a sudden boom the boat just dies like I hit something. After that I get a severe vibration that worstens when the trim is up at all.


Got home there is water in the drive shaft bellows, no apparent damage to prop or ujoints. Gimbal seems smooth. Where should I go from here?

 

[alldodge]

Re: 1993 Merc alpha one vibration

Do you notice the vibration with muffs running on the trailer? If you do what if you run the engine without the drive on does it go away? If you can determine it is the drive and not the engine (which it sounds like) I would suggest taking it to a shop and have it looked at.

 

[ponchoman]

Re: 1993 Merc alpha one vibration

I'm going to do just that. Start it up briefly check for vibrations.

 

[ponchoman]

Re: 1993 Merc alpha one vibration

So I started her up. Starts and idles just fine. No weird noises. But once u increase the throttle the boat shakes with a low tone, around 1200 rpm and like before if you increase the thottle the vibration gets better, but its still there. I have solid mounts

Uhhmmm... Would a misfire translate into a bad hull vibration? Or is it possibly somethig else? When the boat died it was like a big hiccup, then the vibtation came on strong.

 

[CJ0920]

Re: 1993 Merc alpha one vibration

Did the hiccup sound like a spit/backfire? Reason I ask I had the same thing happen to me. Took her out damaged the prop and barely made it back to shore. Put a new prop on this weekend and went out. Had a hard time starting it, when the pull out and boat died as increasing throttle. Same thing, but vibrating, bogged down, spitted and a couple loud pops. I did a few times and off we went, just seemed as though the boat wasn't running great. Got home looked at the motor and noticed the electric choke was just dangling...idk if that's the problem though.

 

[ponchoman]

Re: 1993 Merc alpha one vibration

I dont seem to have misfire, but gonna do compression test just for giggles.

 

[alldodge]

Re: 1993 Merc alpha one vibration

So I started her up. Starts and idles just fine. No weird noises. But once u increase the throttle the boat shakes with a low tone, around 1200 rpm and like before if you increase the thottle the vibration gets better, but its still there. I have solid mounts

Uhhmmm... Would a misfire translate into a bad hull vibration? Or is it possibly somethig else? When the boat died it was like a big hiccup, then the vibtation came on strong.

I don't think at this time your issue is with a mis. Did you try removing the outdrive and runnning the engine by it self, connect the hose to the thermostate housing or directily to the drive housing? If so was this the vibration you mentioned? If you left the outdrive on you really need to try it without the drive. If it happens without the drive I would look at the harmonic balancer, flywheel engine coupler or one of your pulleys (Alt, power steering, water pump, idlers). If the vibration goes away it is in the outdrive or coupler.

 

[ponchoman]

Re: 1993 Merc alpha one vibration

I did try it for a sec with the outdrive off. A vibration is there but clears up as you rev. It was way worse in the water any throttle/ trim made it unbearable. The boat has always had some vibration, but I figured it was due to the solid mounts. The boat had a bad gimbal bearing when I got it, could the engine coupler be worn as well? How do u check?

 

[ponchoman]

Re: 1993 Merc alpha one vibration

Just trying to go thru things while its apart. I pressure tested the lower unit with 12 lbs. it lost one pound exactly over 12 hours. Could have been the equipment, I dunno. Is that acceptable? I rotated the input/ output shafts a few times during this time. It was in an uninsulated garage and it got fairly cool last night as well. May explain the pound loss?

 

[alldodge]

Re: 1993 Merc alpha one vibration

I don't see an issue with your test. Does the end of the input shaft look OK, was there any metal filings on it? Look at the splines of the coupler and see if the internal splines look good. The gimble bearling still good, rotates smoothly? If the internal splines look damaged this could cause a problem but generaly they don't cause a vibration they just burn out and your boat stops moving; that is unless the bolts are coming loose on the coupler. Take an engine alignment tool ( Engine Alignment Tool - iboats ) and it should slide in with ease. Have you had any difficulity removing or installing the drive? Is there any play in the U-joints?

Is your timing still within specs? Harmonic balancer apear to look like the outside ring has not moved?

 

[ponchoman]

Re: 1993 Merc alpha one vibration

Input shaft is good no shavings. None inside coupler as far as I can see. Joints seem perfect, gimbal is smooth. Outdrive came out easy. I'll check timing. Its set to go to the shop next Tues but still wanna rule what I can out.

 

[ponchoman]

Re: 1993 Merc alpha one vibration

Update. It was at the shop for 3 weeks lol. They straightened the prop shaft, new carrier assembly (what is that?) new impeller, bellows, shift cable...hopefully the prop shaft is what it was along with the carrier. Test run sat. They said it tested-ran great. Fingers crossed.

 

[alldodge]

Re: 1993 Merc alpha one vibration

The prop shaft is held by the carrier. I would sure like to know how they managed to strighten a bent prop shaft, or better yet what the heck was hit so hard to bend it. Either way I'll hope all is fixed

 

[ponchoman]

Re: 1993 Merc alpha one vibration

I didn't winterize the drive last fall, and did find water in the first bit of oil. Maybe damaged the bearings in the carrier. Stupid move.