d.i.y service .

toshiba2010

hello
i am going to attempt a full service yamaha 3.5 2 stroke 1980 model outboard . how would i go about doing this and what do i need to complete the job .

this is my first boat/ tender i bought for going fishing. so i know nothing about the upkeep of the motor.

fergal.b

Start off by getting a service Manual for your engine.
They are a very basic engine so not much servicing to do gear oil/spark plug
I think they are air cooled so no impeller but water is forced up to the exhaust when it's moving to cool them so don't sit for too long with the engine ticking over and not moving.





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toshiba2010

thanks fergal yes it is air cooled so it is as simple as that . gear oil and a spark plug . does the plug gap have to be gapped to a certain mm ..

fergal.b

If it's running fine I would leave it alone, the gap should be around .030



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toshiba2010

would the gap between the spark plug make a big difference if it was not gapped properly .. the reason i ask you this question is because i did have the spark plug changed in it and the guy in the shop just took a new spark plug from a box and put it in without gapping it .

also it is running or seems to be running fine but is quite slow on the water can you help .

fergal.b

It shouldn't make much of a difference as long as the tread is the same length, a wide gap will show problems on higher revs like a miss and you might find it harder to start a smaller gap will burn out the plug quicker. If you think it's running rougher than before then try bring the gap down to .30 and see if it helps. A plug can go from .30 to .40 after about 100 hours and still run fine as these older outboards often put out a bit more power from the coil or magnetos.



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toshiba2010

right so thanks .. does it really matter how many turns you give the butterfly nut on top of the petrol cap . if it is too many turns can it affect the operation of the motor . also what is that hole in the leg going down the towards the propeller where the paint is chipped off

fergal.b

It has to be able to take in air so if it has a vent screw make sure thats not tightened down the main body of the cap can be.

The hole might be the water drain or if your talking about a hole covered by a plate, thats used to gain access to where the drive shaft can be separated.







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toshiba2010

for got to ask but where can i bring it for a compression test or could i do it myself what would i need ???

toshiba2010

for got to ask how can i check the compression .

fergal.b

You can get one of these in most motor factors or Halfords "if you can get one with fittings for different plugs sizes" just take out the spark plug and screw it in then pull the engine a few times and that will give you your compression.

toshiba2010

what should the compression be on this motor

fergal.b

I'd be looking for around 100 psi but you might need to check your service manual.





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toshiba2010

dont have a service manual or cant get 1 anywhere . the motor is too old .

fergal.b

This might help you out http://www.autocd.info/autocd/OM/3.5A%20624-28198-E5.PDF




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toshiba2010

thanks fergal for that link could not find one anywhere now i have some idea what i,m dealing with cheers man ...