Mercruiser MC-1: is this play acceptable?

[ratdude747]

While putting my outdrive back together (impeller replacement) I noticed some steering/trim play:

View attachment VID_20240522_211851.mp4

It's a 1976 Mercruiser 888 (MC-1).

This is a project boat that I haven't had on the water yet, so I can't comment on steering performance (it's a standard cable setup, no power assist or hydraulics).

It doesn't have grease zeros on the tilt pins... Only grease points are those the steering pin and for the gimbal bearing (both of which were given 20 or so pumps of marine grease due to the boat having sat for 10 years).

Is this:

A. Not an issue, just keep it lubed
B. Might want to work on it next winter, but it's ok for a relatively light season (or at least a few lake tests?).
C. Game over. Rebuild it before even think of testing it.

 

[dubs283]

Side to side looks normal for an almost 50 year old steering system

Up and down is concerning. Check the lower swivel pin at the gimbal ring, needs to be very little/zero slop between the pin, gimbal housing and bearing in the ring. Bearing and pin are both replaceable. Gimbal housing is not serviceable in that regard

 

[ratdude747]

Side to side looks normal for an almost 50 year old steering system

Up and down is concerning. Check the lower swivel pin at the gimbal ring, needs to be very little/zero slop between the pin, gimbal housing and bearing in the ring. Bearing and pin are both replaceable. Gimbal housing is not serviceable in that regard

From what I could tell, most/all of the up/down slop was in the side pins. But I will recheck after work...

 

[ratdude747]

Appears the vertical play is a rotten trim cylinder bushing

Oddly, it's the only one with a rusty nut. Maybe where my cover drains?

Either way, I should be good to just replace the bushings?

Edit- that's not a stock nut and washer... Looks like an automotive bushing washer&nut. Though that looked too familiar! Good riddance, given that it's submerged!

 

[ratdude747]

Parts came in... and they don't fit. Exploded view I used is wrong?

Bushings are too big. But, having taken some measurements, apparently there are cheap yet good polyurethane shock bushings out there that are the same dimensions:

Energy Suspension 9.8113G 5/8in. SHOCK EYE BSH-1/2 HRGLS – Energy Suspension

teamenergysuspension.com

I also didn't get the right replacement nut or washers.

The nut is a 3/8-24 (NF) 316 SS nylock nut. The outer washer is a 1.5" OD 3/8" ID 1/8" thick 316 SS fender washer. The inner washer is a 1.5" OD 5/8" ID 1/16" thick 316 SS washer. The outer washer I can't get from my usual non-marine sources (fastenal, McMaster-Carr, etc.) in the correct thickness. Needs to be thick to support the bushing. Will see if I can figure out the mercruiser numbers on these and eBay them.

The bad side had no inner washer... and only 1 bushing, badly deformed and rotten. Can't go boating on that!

Edit- Finally found a usable exploded view whose numbers I was able to confirm match the measurements on my actual parts:

https://www.marineengine.com/parts/mercruiser-sterndrive-parts/888-19711977/3106717-and-up/trim-cylinders-and-hydraulic-hoses

Nut: 11-34932
Outer Washer: 12-46765
Inner Washer: 12-45737

Still going to try the Energy suspension bushings. I have their poly bushings on one my trucks that sees some spirited driving... AFAIK no issues. I see other people using similar poly on upgraded bravo bushings, so I figure it's worth a try?

 

[ratdude747]

Parts came in today.

Installing the new bushings was a royal pain. Seems the threaded ends of the shafts were just a touch too short. Had to use friction clamps to get the outdrive ends on.

Yet, it seems automotive polyurethane mY be too soft... As with just enough stud threaded to fully pass the nylon part of the nuts, it seems that a couple of the bushings are too deformed?



Is that OK? Or do I need to pony up the $80+ for actual quicksilver (or "made for my application") bushings?

Also, there is in fact a slight amount of play in the upper swivel pin. Couldn't get it on video, no more than 1/64". That OK? There wasn't any obvious play in the lower swivel pin (which I since found the grease zerk for and flushed the grease in... Old grease did come out, it wasn't dry!)

 

[ratdude747]

After some thought, I'm going to get the "right" bushings... and call these bushings a fail. I am finding they aren't that expensive after all...

 

[ratdude747]

Genuine mercruiser bushings came in. Sure enough, there is about a 1/8" difference:



They seem to fit a lot better. But, despite swearing that there were 8 bushings in the bag, by the time I installed the 7th the bag was empty. Ordered another single bushing. Guess this won't be done today after all!

Despite being softer, the poly bushings are too tough to cut with a utility knife... So no good way to accurately shorten them to match the genuine rubber bushings. Let it be known that despite similar dimensions, polyurethane shock absorber bushings are *not* compatible with older Mercruiser trim cylinders!