Help! How Bad Is This??

[Smesh]

Recently bought this Avon SR4 and got the motor working great. I mean GREAT! The two test runs in the harbor were awesome, but there was this little squeak, squeak at idle in neutral, so today after installing new control cables, I decided to use a socket to see if the motor mounts were loose. I barely touched it and WHAMO!! The fricken nut just fell off.

The first two pics are of the broken bolt. The second is the other side and what it's supposed to look like. It looks to me like one would have to remove the whole power head to fix this, but I bet that any bolt I tried to remove to repair it would also break!

I'm guessing it's not at all safe to run this even at slow speed? Any ideas? This is a 1986 Mariner ML30 and parts are really hard to find. I'm super bummed.

[stevo]

thats an easy fix for a mechanic using a stud extractor or he will drill it out and retapp it for a new bolt

[HughN]

Originally Posted by stevo

thats an easy fix for a mechanic using a stud extractor or he will drill it out and retapp it for a new bolt

I'm not sure that will work. I think the the 'head' of the bolt is embedded in the rubber with another pointin in the other direction into the tray.

They're good engines.

[paintman]

Hugh is correct. It's a big lump of rubber with a threaded part attached to each end. The bolt doesn't go through the rubber. Just looks a bit like a mushroom stuck onto each end of the rubber.
It looks like this (posted as an example pic only): Mercury Mariner Upper Side Mount 82557M 1977-97 25 28 30 35 HP | eBay
You'll find a schematic of your engine if you go here:
1986 Mariner Outboard 30 [ML] [ 7030226] - Parts Lookup - Crowley Marine then left click on the brown 'View components' bar. Go down the menu that appears on the left & left click 'Mounting system'. The part you need is No 17 in the diagram.
Unfortunately it does look like a PITA to fit.

(FWIW there are several similarly constructed smaller mounts on the cowl of my Merc 135 & they are a complete PITA as the metal keeps separating from the rubber. As they don't carry much load I just clean the mating faces up & epoxy them back together. Damned if I'm paying £20 odd each! This is unlikely to work with yours though as it appears yours may have a higher load. I do toy with the idea of just drilling though the rubber & substituting a bolt, but this would obviously affect the anti-vibration qualities of the rubber mount.
There is a square portion on each thread which fits the hole in the engine to stop one end turning as you tighten the other so with this type of mount if you can't get at both ends - as would be the case with a bolt - tightening could be a problem as the bolt may just spin unless you can use another way of preventing that. A longer exposed thread on the exposed part could be gripped if you use a normal nyloc nut instead of the acorn you currently have.)

ETA and NB! On the standard mount the nuts at each end are only intended to be nipped up. Continuing to tighten beyond that point won't do anything to the rubber part but will shear the end off the thread.

[uncle al]

Dont be down hearted, that is just a minor snag. Those engines are old but bloody good. Our MOD ran them for years.

[Smesh]

It's hard for me to figure out, but it looks like much of that load is for the grip and tiller mounts. Am I wrong? The tiller hand is NFG as all the cables are seized and the shift shaft fell apart inside it. That was one of the first things I tried to take apart and one of those bolts broke immediately. No big deal there, so I just left it. Fast forward two months and my brain forgot to be careful of seized nuts/bolts. I just use the controls and don't worry about the tiller handle so no biggie.

I'm not sure if that mount is really taking any weight or not or if there is any danger of the motor falling into the sea. At least knowing there is another head holding it from the inside helps. Taping the bolt might be a good idea if not holding a lot of weight. Otherwise, Removing the powerhead to get access will most definitely mean a lot more broken seized/broken bolts and a massive PITA.

[paintman]

Issue will be how the engine is attached to the steering pivot shaft. If those two mounts are the only attachment for the top of the engine then it could be an issue as the broken side could fret, if they don't then it won't be.
Needs someone who has had one apart for the answer.

I wonder if a threaded stud could be welded onto the broken end in situ? Be worth speaking to an engineering company local to you.

https://www.youtube.com/watch?v=gWymKHVABKo

[jeffstevens763@g]

Originally Posted by paintman

Issue will be how the engine is attached to the steering pivot shaft. If those two mounts are the only attachment for the top of the engine then it could be an issue as the broken side could fret, if they don't then it won't be.
Needs someone who has had one apart for the answer.

I wonder if a threaded stud could be welded onto the broken end in situ? Be worth speaking to an engineering company local to you.

its called stud welding done that for a while would be too tight to get the ceramic in which holds the weld plus too much heat generated and would burn the rubber.

[jwalker]

It's a rubber engine mount and you need to replace it. The rubber is attached to a steel plate at either end and the steel plate has a stud as part of its structure. That stud on yours is sheared off.

You need to screw the rubber part out of the block. Its a bit tricky without removing other parts, but it can be done providing it too is not seized into the aluminium. Be sure to lubricate the threads with water resistant grease on reassembly.

If you find it impossible to remove it in situ, just be patient and work away dismantling whatever is necessary, remembering to use that grease on every thread on reassembly.

[paintman]

Originally Posted by jeffstevens763@g

its called stud welding done that for a while would be too tight to get the ceramic in which holds the weld plus too much heat generated and would burn the rubber.

Thanks. I did wonder.

[paintman]

Originally Posted by jwalker

You need to screw the rubber part out of the block. Its a bit tricky without removing other parts, but it can be done providing it too is not seized into the aluminium. Be sure to lubricate the threads with water resistant grease on reassembly.

Parts diagram & the pic of the part shows a nut at each end of the mount instead of a thread cut in the driveshaft housing for it to screw into.
Is it the case that its actually a captive nut inside the housing - the unbroken end - & the square portion at the bottom of the thread on the mount is free to turn & not locked in to a similar shaped hole which would prevent turning? If it's not a captive nut then it either won't come off once it's loose enough to turn or it will fall off inside the housing & - assuming it isn't accessible without taking a lot of other stuff off -then how do you get it onto the new mount?
As I said earlier, my experience of this type of mount is that the nuts are not captive & the square part fits into a square hole - visible on his pics of the broken one - which prevents the mount turning as it's being done up.

I'm guessing that you might have done this on one of these engines & if that's the case I stand to be corrected!

[phantom 19]

There is a nut on the inside of the leg. You have to strip it down to sort it.

Usually those two side mounts are fine, it is the front mount which lets go and causes the tray and engine to rattle around at idle. The front mount is visible through a hole under the lower tray - you will see a nut there and you will be able to see if it has let go.

I have rebuilt dozens of these engines over the years (it is based on the original Yamaha 20/25/28hp. they are an excellent engine and far preferable to Yamahas later twin carb 20/25 autolube "high tech" range.

Their only real weakness is there is a small recess on the block casting by the lower cylinder liner to accommodate a head bolt and still leave a full width for the waterway. Corrosion attacks this point and gets between the liner and the block and can either split the alloy causing head gasket leak or actually ovalise the liner causing the lower piston to nip up at tdc.

[jwalker]

Originally Posted by paintman

Parts diagram & the pic of the part shows a nut at each end of the mount instead of a thread cut in the driveshaft housing for it to screw into.
Is it the case that its actually a captive nut ......

Yes, you've brought it back to mind, it is a nut but not a captive one. Apologies for the bum steer. I think I've got an old casing somewhere, if I remember tomorrow, I'll take a pic of the inside for you.