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What to do - 1978 Mariner 55 hp (2 cyl built by Yamaha)

wynjim55

wynjim55

Regular Contributor
After having the boat out for it's first run and having it fail a number of times I figured it was time to delve a little further. The engine seemed to run fine at idle but wouldn't rev out passed mid range. It opened up and ran perfectly for less than a minute before dying again. Eventually when we had limped back into the marina it refused to start.

Since then I've cleaned and put a kit through the carbs and fuel pump, replaced all the fuel lines and clamps, and had the carbs synchronised by the local Yamaha dealer. On picking it up I was surprised by how cheap it was but somewhat deflated when he said he thought the crankshaft seals seem to be worn and that the engine seems to have trouble sealing to draw the fuel through the system. Once he got it started it ran and would even start after being switched off, but he seemed to be saying it might last ages or not go anywhere.

He said they wouldn't be interested in doing the work to replace the seals and after previously fighting with a lot of the stainless bolts in alloy housings I can see where he is coming from. I still intend to take the boat out for a run to see how it goes.

Should I be taking the risk on this engine leaving me stranded? I only intend staying in the relatively sheltered waters between mainland Australia and Fraser Island. Naturally a new outboard would be an ideal situation but I can't see that happening any time soon.
 
Re: What to do - 1978 Mariner 55 (2 cyl built by Yamaha)

Have a Merc 110 in the shop that needs crank seals so bad it doesn't make enougn vacuum to pump fuel. Sounds like yours. DON'T keep running itthat way or you'll trash the block.

Jeff
 
Do a compression test before you do anything.Then start at the tank.Check for air leaks and the vent line for plugs.
Check for water in the tank.Do these thing and post the results.J
 
Powerhead removal is easy, sacrifice the bolts mate. Just turn them till the heads break off, or cut the heads off. When the powerhead is out, they are dead easy to remove from the block, just heat block with propane and they turn right out. I just replaced teh bolts (which are chromed steel, not stainless) with cad plated grade 8 bolts. I intend to replace them every two years.
Anyway, forget the dealers for a rebuild and ordering parts, contact Golden Seal in Melbourne. I got a Mariner genuine rebuild kit and rings for my 60 for under $250 from them, every seal you could ever need is included. If you know how to use a torque wrench, you can easily rebuild this engine.
 
I thought the powerhead was held by studs with an exposed nut per stud. I undid them easily but the powerhead would not oblige. Did I miss some bolts?
 
Gaskets are gluing it together. Try prying upward on the studs with a screwdriver wedged between the stud and the driveshaft housing.

Jeff
 
Make sure you get all the studs too, I think tehr are eight or nine. Three each side and three around the front, between swivel bracket and leg. Then there WILL be some corrosion around the studs. Applying a vertical load to powerhead (like an engine hoist) whilst tapping on studs with a centre punch will help with the corrosion, as will liberal amounts of oil. I got mine to let go by leaving it on the engine hoist for a week and gave it all a good tap and some heat every night.
 
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