Boat Engines etc - Maintenance and Repair

2 stroke outboard servicing

by sprocker » 03 Apr 2018, 09:50

We inherited an Avon RIB with a 15hp Yamaha 2 stroke outboard when we bought our new boat, The Yamaha is of indeterminate age at the moment but I suspect around 15 years old. I will check that as soon as I can get to the serial number.

The outboard is running OK at the moment, but the previous owner didn't remember when it was last serviced.

So I want to give it a full service, just so I am starting the season from a known datum. This is my first 2 stroke outboard for over 20 years, and the old grey matter cannot dredge that far back.........

Can anyone offer advice, or point me in the direction of information regarding what should be done during a full service, and possibly how to do it?
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by Ianfs » 03 Apr 2018, 21:16

Hey Andy.
Me too with small outboard engines. Internal combustion engines can't have changed that much though.

What do you think? 2 stroke oil is mixed with fuel, so no need to change it.

So gearbox oil, plugs, impeller. Really that must be it.

After that maybe if necessary carb rebuild, impeller housing rebuild. Trouble with carb rebuild is they can cause trouble. So if it runs ok leave well alone.
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by sprocker » 04 Apr 2018, 07:28

Thankyou Ian,

Gearbox oil, plugs and impeller was pretty much what I thought. Along with emptying and cleaning out of fuel tank, and re-fill with clean fuel/oil mix.

The carb was an unknown to me, but having thought about it I do agree it is probably best left alone unless it is causing issues.
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by shibbs » 04 Apr 2018, 12:06

Thought I’d add a little.
I had a few issues with my little 2.2hp a couple of seasons back.
My problem was clearly down to the impeller not pumping.
When I stripped down, I was amazed at how little there was to it. Having worked on 2 stroke bike engines in the past I had an idea of what to expect but it was amazing how simple the engine was.
Anyway, whilst my impellor was shot to bits ( due to being 15 odd years old) the main point of the problem was the fact that all the cooling waterways were pretty much blocked due to salt. This still occurred even though the engine was always run up in fresh after use.
So, might be worth checking that if your taking apart.
WRT service though, I really would agree with the points above, and if running, don’t delve too deep..
If it ain’t broke and all that!
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by ColinR » 04 Apr 2018, 14:25

In the olden days when I had a 2 stroke bike it really benefited from a top end de-coke on a regular basis. Simple job of removing the head,and scraping the charcoal from the piston and head. Try not to let the debris get between the piston and bore though as scratches will lose you valuable compression. The smoother the head and piston the better.

A tip is to get the piston to the top and smear grease between the piston and barrel. Pushing soft string in the same place also works.

We used to cut a new head gasket from a cereal box but I suspect there is a more modern high tech alternative nowadays :lol: :lol: :lol: :lol:
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by sprocker » 05 Apr 2018, 12:34

Good point on the salt build up Stu, I will look into that, and I agree wholeheartedly with 'If it ain't broke don't fix it' !

Colin, I don't think they make Cornflake packets quite as thick theses days, so would probably look at purpose built gasket material.......
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by ColinR » 05 Apr 2018, 15:01

Probably a wise move :D
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by sprocker » 05 Apr 2018, 20:20

Having said that....I opened a new packet of Scott's Porridge Oats this morning.......now there is gasket material!
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by Ianfs » 06 Apr 2018, 07:25

Not heard of Oats used for gaskets . :lol:
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by ColinR » 06 Apr 2018, 08:25

Interesting concept. Maybe mixed with some Red Hermatite and gently baked for 30 minutes under pressure. :mrgreen:
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