How much cooling water should come out of back of small outboard?

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Ric

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I've been servicing my dinghy outboard - a tiny Yamaha 2-stroke 2hp engine - and have been running it in a tank to flush it through with fresh water.

How much water should come out of the cooling outlet vent? There is no trickle - just lots of spitting of steam, with the odd spurt of a couple of drops.
 
My small O/Bs have usually emitted very little water when idling but a reasonable stream at higher revs, though often rather dispersed with the exhaust gases. I tended to put my hand near the outlet to collect the mixed exhaust and water to judge the amount better. It sounds as if yours is not emitting enough. It is fairly easy to get the head off and clean the passages nearby, though harder to take the motor off the shaft to clear the main bits. It may also be a problem with the impeller but blocked waterways seems commoner.
 
Ric said:
I've been servicing my dinghy outboard - a tiny Yamaha 2-stroke 2hp engine - and have been running it in a tank to flush it through with fresh water.

How much water should come out of the cooling outlet vent? There is no trickle - just lots of spitting of steam, with the odd spurt of a couple of drops.
Click to expand...

All O/Bs I've used from 2hp to 30hp, both 2 & 4 stroke, have had a steady stream of water from the outlet.

Sounds like you have a partially blocked internal passage somewhere - not uncommon for a small O/B used in salt water. There were recent posts about this.

http://www.ybw.com/forums/showthread.php?t=257793

http://www.ybw.com/forums/showthread.php?t=252184&highlight=outboard
 
should be flowing like the sculpture of a little boy pee-ing into the pond

sorry that all the advice i can give
 
Ric said:
I've been servicing my dinghy outboard - a tiny Yamaha 2-stroke 2hp engine - and have been running it in a tank to flush it through with fresh water.

How much water should come out of the cooling outlet vent? There is no trickle - just lots of spitting of steam, with the odd spurt of a couple of drops.
Click to expand...


My 2hp Mariner is just the same and have been told this is normal, certainly no problems experienced in use since purchase last April.
 
Can you make out the stream in this pic? Just to the right of the leg. The motor has it's cover removed after I'd cleaned out the water passages. It's a Tohatsu, which is the motor most small 2 strokes are a re-badged version of.

tohatsurepaired2.jpg
 
Yep if it has a pee hole ( not all do) then it should be a good steady stream.

You should also see some water from the exhaust pressure relief ports in most cases too.

The pee stream is usually just a telltale. If its hot, as opposed to warm, it's a bad sign.

Steam is a very bad sign.

You should be able to touch and maintain contact with the cylinder block for two or three seconds at least If you cant its getting too hot. If a splash of water sizzles and boils its definitely too hot. If the paint discolours it is in trouble!

But I did not think a 2hp Yamaha had a pee hole!
 
One man's experience. My 2 horse Yamaha didn't leak water from the block on the shaft, got too hot to touch, and tended to stop after about 10 minutes running. The impellor had half a blade left but after fitting a new one it happily leaks water from the block, can be picked up without burning fingers and runs until the fuel runs out. Impellor and kit including new pump body and seals cost ~£42 and was easy to fit.
 
We are all assuming that you have checked the pump rotor. If not do it and check the rubber seal between the outlet pipe from the pump and the powerhead. If these are OK then the worst possible outcome is that the internal waterways are blocked. You should be able to hold your hand in the stream
 
Youtube has plenty of examples of all the usual outboards.
Click to expand...
It appears from the YouTube videos then that the 2 hp Yamaha does not have a peehole telltale but should spray plenty of water from the exhaust back pressure relief ports on the back of the leg although I think there should be a cover over these that deflects the water and exhaust downwards.
Part #6 in THIS DIAGRAM
 
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If your Yamaha 2 is the same as my Mariner 2, there is no direct outlet. There is a relief hole part way down the leg but the water that exits here is only a 'mist'. The cooling water 'free falls' down the leg and is blown out of the relief hole as it passes.
See here for some pictures... http://www.troppo.co.uk/odds/Mariner%202M%20Impeller%20replacement.pdf ...last photo.
 
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