Just got an old air cooled Yamaha 5 HP

Patrik · 15 July 2011, 23:44

Hi

I've just bought (had to buy to get the boat) an old Yamaha 5 hp. It's probably from the 80's, and it's air cooled! All my previous engines has been water cooled, what's the difference? Why are there even air cooled ones?

The problem with it is that the spring that pulls back the rope after starting (don't know the terms for these things) doesn't work, so the rope will keep hanging outside the engine.

Otherwise it's been said that it should work very well. It hasn't got a built in tank. Is this engine any good or should I try to get rid of it right away?

Poly · 16 July 2011, 00:00

Quote:

what's the difference? Why are there even air cooled ones?

Air cooling has some advantages - most specifically that there is no cooling water circuit to fail (broken impeller, blocked intake, salt in water passages etc) which is one of the more common causes of catastrophic premature outboard engine death! [In theory the air cooling fan can fail too but this seems less likely to go unnoticed, and without proper maintainence as it is easier to access]. I'm not sure what all the disadvantages of air cooling are but the most obvious one will be the horrendous noise!

The main difference from a user perspective is that the engine runs hotter so is probably intended to use scooter/chainsaw/lawnmower 2 stroke oil rather than normal (TCW3) outboard motor oil.

Patrik · 16 July 2011, 00:15

Hehe! I see, useful info. Practical that I won't need a bucket to test run it at home...

Nos4r2 · 16 July 2011, 00:37

Quote:

Originally Posted by Patrik

Hehe! I see, useful info. Practical that I won't need a bucket to test run it at home...

Actually, you might. Some aircooled motors had an impeller (thinking back to the Volvo penta aircooled 5hp) that's purpose was to pump cooling water through the exhaust to keep it from getting so hot it blistered.

Exactly what model is it? Got pics?

Fenlander · 16 July 2011, 11:02

Is it the 5hp version of this one Patrik?

‪Yamaha 3,5 km‬‏ - YouTube

5hp looks just the same as the 3.5, I had one in the 1980s as a river engine for a 16ft fishing boat. Basic, reliable and very noisy. Just forward and neutral so you had to spin it right round to go in reverse, that's why it has a handle that goes right round.

Can't remember the exhaust cooling issue.

Patrik · 16 July 2011, 23:02

Quote:

Originally Posted by Fenlander

Is it the 5hp version of this one Patrik?

That was mad noisy!!

However I'm not sure it would be useful for me at that sound level, can't even go back to the cabin with that one after eight at night

EDIT: hmm found a picture of the engine, doesn't look as similar as I thought. I attach it.

Patrik · 17 July 2011, 10:21

Now this looks more like it!

‪Yamaha 5BS testvaart‬‏ - YouTube

spartacus · 17 July 2011, 11:56

Quote:

Originally Posted by Patrik

The problem with it is that the spring that pulls back the rope after starting (don't know the terms for these things) doesn't work, so the rope will keep hanging outside the engine.

Otherwise it's been said that it should work very well. It hasn't got a built in tank. Is this engine any good or should I try to get rid of it right away?

The fact the starter rope doesn't retract is probably a broken coil spring. If you're replacing the spring - then replace the starter rope too. Could be corrosion simply due to sitting around or general wear and tear from starting over the years. Not sure if Yamaha even sell the springs - or you could salvage one from someone that's breaking a similar engine. When new - they normally come with a film of machine oil on them. Without undoing the coil (important), lube up with a marine grease.

Regards getting rid - I'd have thought you'll be hard-pressed to find a buyer.

Poly · 17 July 2011, 12:28

Quote:

Originally Posted by spartacus

Regards getting rid - I'd have thought you'll be hard-pressed to find a buyer.

People buy any old motor on eBay. If the spring was fixed then I'd be surprised if it went for less that 100 pound.

spartacus · 17 July 2011, 12:35

Quote:

Originally Posted by Polwart

People buy any old motor on eBay. If the spring was fixed then I'd be surprised if it went for less that 100 pound.

True.

Patrik · 20 July 2011, 00:37

Now the problem seems to be to find a spring for it! I went into the best repair place in our city and they said it wasn't possible to get those old springs. However the specialist was on holidays for another three weeks. Would love to find a way to fix that thing, couldn't it be possible to fix with a spring for some other engine?
Or if I could find a spring on here or on ebay. How would I find one that matches?