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Old 09 May 2021, 10:49   #1
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Stuck bolts on yam 15 2stroke

Afternoon.

The outboard is new to me and I'm working through it giving it as sound a service as possible.

I've just gone to remove the gearbox/prop housing so as to replace the water pump impeller and none of the 4 bolts are wanting to move. They definitely give the impression that any additional pressure and they will sheer.

Any tips on safely loosening them?

Thanks.
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Old 09 May 2021, 11:08   #2
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Bit of careful heat which can ease the bond of threadlok if that’s been used and helps generally. Sharp but sensible taps on the bolt heads with hammer. Even if you turned the OB upside down penetrating oils probably little use.
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Old 09 May 2021, 11:59   #3
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Thanks. I assume gently heating it to the point of being too hot to touch is about right?
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Old 09 May 2021, 12:16   #4
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I'm assuming they are a flanged head setscrew. In that case put the socket on an impact driver and try that. You can't use strong heat because of the paint finish.

Otherwise I wouldn't be too fearful about them shearing as that is easier to deal with than if the hexagon heads round off.
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Old 09 May 2021, 15:13   #5
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Originally Posted by TmMorris View Post
Afternoon.

The outboard is new to me and I'm working through it giving it as sound a service as possible.

I've just gone to remove the gearbox/prop housing so as to replace the water pump impeller and none of the 4 bolts are wanting to move. They definitely give the impression that any additional pressure and they will sheer.

Any tips on safely loosening them?

Thanks.
Ring spanner + rubber mallet. No point using penetrating fluid. Sharp knock to free it, then tap the other way. Takes time, it breaks it breaks but I think what we're dealing with here is an engine with no history. Not sure if a Yammie 15hp has a 5th bolt under the trim tab?
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Old 10 May 2021, 04:10   #6
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Thanks everyone. Steady heat from the kitchen butane blow torch released the bolts. Then I remembered the steam cleaner for heating up the 4 bolts holding the impeller. All clean now just need to start the hunt for the silicone grease!!
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Old 10 May 2021, 04:34   #7
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All clean now just need to start the hunt for the silicone grease!!
Use sparingly. Real life experience from another forum, if any clumps of grease lodge in small water passages, then sand can get trapped and overheating problems can ensue. At least yours is easily rebuilt but not so with a bigger four stroke.
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Old 10 May 2021, 05:19   #8
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Thanks. Good advice. At this rate there will be no extra silicone going on.
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Old 10 May 2021, 07:09   #9
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Well done on getting them out.... always a good feeling when all the bolts are free.
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Old 10 May 2021, 07:49   #10
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Certainly was a good feeling until it came time to reassemble.

All went back together but came to realise that the gearbox is jammed in reverse.

The linkage on the foot, down into the box won't budge at all.

I have a feeling that this could be my own fault in that I'm waiting for the fresh gearbox oil so it is currently drained and when removing the foot I was selecting gears to reveal the linkage nut!!

So I think the jam is in the box and this has revealed another minor glitch, screw off, two nuts undone and I cannot for the life of me prize the front of the gearbox off. Does that plate swivel or is it located? Ie can it be tinkled with a mallet to get it at least rotating?
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Old 10 May 2021, 08:41   #11
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I never had to remove the front of the gearbox on mine. I think Oldman2 on here has a workshop manual for that motor and might be able to look it up for you to see if there is a method.
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Old 10 May 2021, 08:47   #12
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I've done it on the smaller units but they've never been jammed and just prise off easily. This one is pretty solid and may need a puller on it.

The real issue is why the gear linkage has jammed. It's absolutely solid. Usually you get loads of warning that there is an issue just from the feel when putting it in gear but this one felt great which is why I'm scratching my head wondering if I've done something but I can't see how.
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Old 10 May 2021, 09:20   #13
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I have found often reverse is a hard gear to get in/out if the engine isn't running should you have a need to do that... and I usually just ease the prop/splines round a little then it will slip in/out of gear easily.
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Old 10 May 2021, 09:26   #14
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Here is a video that may assist


I wonder if there was some debris in the gearbox held in the gear oil, now its drained and been turned maybe upside down, something has dropped into the dog clutch and jammed it. I wonder if a flush or 2 with light oil along with a bit of jiggling of propshaft/gear select rod can release anything that shouldnt be there.
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Old 10 May 2021, 11:40   #15
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Many thanks. Will have a watch. Spent the last hour getting in and finally managed it. While doing so I noticed an oil leak from one of the holes below where the gear linkage enters the box so I'm guessing a seal has gone and frankly all the seals look like they need doing. Plus, the ally block that the water pump sits on has rotted around the drive shaft so needs replacing.

The internals are in good order so I suspect this motor spent years on the davits and was rarely flushed, if ever.
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Old 10 May 2021, 17:00   #16
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Above the wash and upper oil screws are three parallel holes, about 3mm in diameter. At least one is a blank but two seem to pass through into a cavity.

Does anyone know what they are actually for?

On my outboard the leading hole has some black plastic sheared off and blocking it but one of the others appears to be leaking gearbox oil but I've been running the engine in water and there was zero evidence of ingress into the oil.
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Old 11 May 2021, 12:16   #17
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Well, someone has been leaving their outboard with salt water sitting in it for the last twenty years!

There wasn't much crud in the leg but I've never seen a bearing carrier this rotted!!

Full strip underway and sourcing of parts to do a complete rebuild. Gears and moving parts all in good condition but seals all on last legs.

This all ties in with this engine sitting around without an anode for quite some period I suspect.
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Old 12 May 2021, 13:57   #18
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All parts on the way but that bearing plate is not budging at all.

The water feed pipe is bolted on to the underside but it looks implausible to get a spanner on, giving the impression that the pipe will come free with the plate.

Wondering if there is enough space to get a puller down the shaft but other than that it's looking a bridge too far at this moment.
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Old 12 May 2021, 14:19   #19
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Running a bead of weld around the inside of the bearing race will shrink it and the heat will help get it moving.
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Old 13 May 2021, 11:06   #20
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Well, the top section of the bearing plate is free!

Now I just need to work out how to free the bottom part.

On the bright side, I now know all three weep holes lead to the gear selector chamber. Those parts are out but look in perfect condition so not sure how gear oil was coming through but water not going in to the gear box. Will replace the boot and nylon egg seal anyway.
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