Mariner/Yamaha 55 help

[Royb91]

I have a mariner/Yamaha and it is getting incredibly hard to pull start. I'm wondering where the compression release is on this motor. I don't know the exact year but I think it's a 78 55hp 2cyl.

 

[carholme]

Re: Mariner/Yamaha 55 help

Do you have the s/n of the engine?

Gerry

 

[Royb91]

Re: Mariner/Yamaha 55 help

Serial: 594277
Model: w55ml

 

[carholme]

Re: Mariner/Yamaha 55 help

There should be another series of numbers in front of the s/n you have provided. Can you check and see if there is a 663 in fron?

Gerry

 

[Royb91]

Re: Mariner/Yamaha 55 help

663 L 594277 sorry about that

 

[carholme]

Re: Mariner/Yamaha 55 help

You always discount the letter/s in the middle.

Therefore, s/n 663-594277 comes up as:

55 ML 663-580461 - 1985 Marathon

From here:

Mariner 40-55 hp, produktions?rslista, modellguide

Parts List:

55 HP - Mercury, Mercruiser, Force, etc. Parts Lookup

I don't think you will find that there is a compression release valve. There may be a problem with the Lower unit or the power head. You could drop the LU and then try a pull to see if it is normal, indicating you have a problem in the LU. If there is no change, I would remove the cover, item 33 under CRANKCASE AND CYLINDER HEAD and you will get a good look at the pistons for any scuffing and be able to test that the rings are free, using a screwdriver to see that when pressed, they spring back. If that is normal, then I would remove the cylinder head and you will be able to see how the cylinder walls look. Have you done a compression check yet?

Gerry

 

[Royb91]

Re: Mariner/Yamaha 55 help

Went through everything and it's much easier now. I have two questions tho.

First one is where is the low speed jet for this motor?

And second does anyone know where around should I start setting wise on the h/s jet?

 

[MH Hawker]

Re: Mariner/Yamaha 55 help

Both are in the carb. the high speed is fixed and has no adjustment. The low speed is known as the air mixture screw and effects the idle and the basic setting is 1 1/3 turns from lightly seated but it will need to be adjusted on the water not on muffs or the tank.