86 Mercury 35 HP vibration around 1/2 throttle and up

[HeliChopped]

The 35 HP Merc on my pontoon starts to vibrate around 1/2 throttle and up. I discovered if I push down or pull up on the engine cowling vibration noise will go away. A rubber strap hooked between the cowling and fence will solve the problem but the higher the RPM the tighter the strap needs to be. Compression Ok. Engine runs great.
The pivot has alot of play on the lower end like the pivot shaft is to long. Not like a bushing is worn but the mount moves up and down about a 1/4 inch when I move the lower end front to back. I dont see a way to tighten the mount. Any body experience this sort of thing? I have ran out of ideas. TIA

 

[carholme]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

What is the s/n of the engine?

Gerry

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

The tag is no longer legible. The tag is blank in the SN area like no SN even existed. Would it be stamped somewhere?

 

[carholme]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

See if you can find a disc like this on the lower right side of the block:

http://imageshack.com/a/img84/8224/391496208.jpg

The numbers on it will be the s/n.

Gerry

 

[MH Hawker]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

As a guess its from the prop.

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

Serial # A951314.
Replaced prop (new), transom, bolts in engine pod (some loose) and tune-up. Nothing worked so far.

 

[carholme]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

That s/n comes up as:

MERCURY - ( 35 H.P. (1986 ))
Serial No: 0A951314 Model No: 1035716

Parts list for model 1035716:

35 H.P. - Mercury, Mercruiser, Force, etc. Parts Lookup


When you say, "The pivot has a lot of play on the lower end" are you referring to item 18 or item 11 in the attached link from the parts list:

Mercury, Mercruiser, Force, etc. - CLAMP AND SWIVEL BRACKET (NON POWER TRIM) - 35 H.P.

Gerry

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up


Bottom yoke 43 is sloppy loose on shaft 18. I can get a 1/4 gap at the arrow. Maybe it's not the problem but I'm out of ideas.
I thought maybe someone may have come across something like this before.

 

[carholme]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

That is not an uncommon wear point on Mercury engines. The top and bottom grease seals, item 27 are probably well worn and the lower engine mounts are probably well on their way as well, item 26 under DRIVE SHAFT HOUSING. You can remove cover, ite, 33 and clamp, item 29 to have a look at the lower mounts.

As well corrosion does a good job on the yoke and swivel pin splines.

Gerry

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

Are there any remedies for the yoke and swivel pin splines besides 'unavailable' parts replacement?

 

[carholme]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

Bit early to start worrying about parts availability. You have to take the part numbers and go searching online. As well, depending on how bad the damage is to the splines, if there is any, there is some re-conditioning you can do. Most of the play you are experiencing at the moment is due to the upper and lower grease seals which are probably pretty banged up. It is quite a job to dismantle the engine to the point that the swivel pin comes out but it will be worth it when you are done.

The first thing to do is have a look at the lower mounts and see how much play is there as this contributes to the play from worn grease seals.

Gerry

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

The lower mounts have cracks in the rubber but are still in one piece. A search only turned up used ones and since I already have used ones it will have to do.
I will put new seals and do something about that loose yoke. Thanks for your time. I'll post the results when I'm done and tested.

 

[HeliChopped]

Re: 86 Mercury 35 HP vibration around 1/2 throttle and up

It's torn down, parts have arrived with NEW lower mounts. If anyone has a cure for the yoke splines I'm all ears.
The wear seems to be more of a rocking issue. The machinist at my work place didn't know since the yoke is cast that's probably where it's worn but it doesn't seem so bad now the motors apart.
The lower mounts may take care of the problem but I would rather address the splines while it's apart if I could. TIA

 

[HeliChopped]

Well I got the pontoon out on the water just in time for the end of the season. Replaced the seals and all 4 motor mounts. Everything OK now. Engine runs sweet. Found one of the motor mounts outer aluminum shell was egg shaped. Couldn't see a cause for it, no odd ball wear or anything like that but it's fixed. Thanks for the help gang!