exhaust on yamaha 2 stroke 15hp

[stuartgsd14]

My new (to me) 15hp yammy outboard 2 stroke is pretty smokey am i wrong in thinking that exhaust should be coming out under the water? as it seems to be coming out at the back of the engine near the water/cooling exit ....hard to see as it is in a well and not able to remove (prop to big)
I have put to much oil in as I thought it was 50/1 and it is 100/1 so that has made it worse..
would appreciate your comments
cheers
stuart

 

[VicS]

There will be a small relief port in the back of the leg from which some exhaust gas blows .. probably also with a little water, maybe only a fine mist.

The exhaust gas from there often causes problems with engines in a well as they tend to breathe in their own fumes!

It'll smoke a bit because it is burning the oil in the fuel but given a good run it should not be very much.

Its bound to smoke more running on 50:1 than 100:1 but if it were mine I'd run it on 50:1 unless there was a good reason not to... you may well find 50:1 is recommended for commercial use!

Be sure to use a good TCW3 2-stroke outboard engine oil.

 

[CreakyDecks]

I've got three different small two stroke outboards and all of them blow exhaust and water out of small holes in the back of the leg. One blows a jet of water, the others just a bit of spray. I think it is so that you can feel its temperature with your hand to check the cooling system is working. It should just feel warm. As you say most of the exhaust and cooling water comes out at the bottom under water.
I would mix the 50:1 mix with the same amount of neat petrol before running it again. Outboards should only really smoke when they first start.
If it is smoking really badly it might have been given a dose of SeaFoam by its previous owner.

 

[stuartgsd14]

outboard

Thanks Vics the fumes are,as you say causing a problem mostly with me breathing them in.Will try a proper oil as you mention,only using normal 2 stroke it clears when revs are high but yesterday when we got in a little rough water in the wash it started smoking again something to do with it working harder and coming out of the water due to waves maybe.
Also was concerned with the water flow from the cooling pipe outlet so removed the cover and pulled the plastic pipe,plenty of water coming out so i just routed it over the side of the engine and left cover of seemed to work ok i presume it is just an outlet and does not recirculate anywhere?
Thanks for your help
stuart

 

[stuartgsd14]

2 stroke

Have found an online manual for the engine and it seems to confirm that the pipe is just a cooling exit so no problem there.will try and get my hands on some yamalube oil as it is their recomended oil.

 

[VicS]

You may find a bit less smoke using a TCW3 oil. It's formulated for water cooled engines whereas ordinary 2 stroke oil is formulated for air cooled engines, which run hotter, and is a bit heavier. Quicksilver is the most readily available brand. "Premium" is the normal grade but they also do a ( more expensive) "Premium Plus" grade which they claim produces less smoke.

The cooling water telltale is just that. It is an indicator that the pump is working and that water is reaching the engine. I'd leave it connected to the outlet fitting as that may restrict the flow being diverted from the main cooling system through the telltale.

Some people manage to rig up a system to divert the exhaust gas from the relief port overboard. That may help your breathing although when idling you'll probably still get gases rising from the underwater outlet into the well.

You may, depending on age ( engine's not your) be able to view an owners manual and also a parts list and diagrams at http://www.yamaha-motor.com/outboard/service/servicehome/home.aspx

I hope the difficulty removing the engine from the well wont prevent you from changing the gearcase oil annually!

 

[stuartgsd14]

yamaha 15hp

Only just lifted the boat into the water and will be coming out again soon so will change the oil then (promise)just wanted to give it a few test runs as its new to me to before tlc over winter.
Seriously thinking about upgrading to a four stroke outboard for less noise and less smoke although another route would be to mount the engine on the transom as it would be further away and the smoke would be able to clear would need a fairly hefty bracket but worth a try maybe.

 

[stuartgsd14]

yamaha outboard

Glad to report that after obtaining a better quality oil and mixing at slightly over 100/1 she is running nice and clean now.Think she had been standing a while and needed the cobwebs blowing out.