General question about older 2 stroke OMCs

[choppermn27]

General question about older 2 stroke OMCs
Do most of these drip a small amount of gas through the exhaust after going full throttle?
Here's my issue, I've noticed when going very fast 20mph down to a stop I'm seeing a lot of gas out the exhaust.
This is an old 2 stroke OMC 18 HP, and I've been putting off having it looked at it's a 1950s power head on a 1972 housing.
Also it doesn't drip much at all when in a tank, this seems to only happen on boat.
I brought this to the same mechanic who rebuilt my other 18 and he said, it works fine, no leaks when he ran in his tank.
I've got another 18 of similar everything and this was rebuilt with new carb kit, new fuel pump and lines, and this one doesn't leak at all hardly. This one is a 1963 complete unit.
I just don't want to put 250 into this motor if there isn't any resolution with gas seaping out.
The other difference here is the leaker seems to be more powerful with more top end throttle than the rebuilt one.
Any comments are appreciated here.

 

[jbjennings]

Re: General question about older 2 stroke OMCs

Mine don't leak anything as far as I know. I do notice that after I trailer it, there will be some black greasy fuelly stuff ooing out the drains in the lower unit, but not much.
JBJ

 

[choppermn27]

Re: General question about older 2 stroke OMCs

thanks, the rebuilt 18 seeps a bit of unburnt oil, but this isn't anything like other, I may very well just have it rebuilt correctly anyways. We are talking a about the amount of gas coming out is not a lot, but in the water you can see, and smell it.

 

[James R]

Re: General question about older 2 stroke OMCs

Are you sure it is gas and not lower unit oil that you are seeing.

 

[F_R]

Re: General question about older 2 stroke OMCs

Visable gas out the exhaust usually happens during/after idleing for awhile, not running at full throttle. High speed running generates enough exhaust heat to burn or at least evaporate it. Somethng is fishy there and it isn't the bass.

 

[coolguy147]

Re: General question about older 2 stroke OMCs

lol^

 

[choppermn27]

Re: General question about older 2 stroke OMCs

No, you cannot see gas when at high throttle/speed
No it's not oil it's gas because you can literally smell it when killing the motor it almost seems worse when you use the kill button vs running the gas out by popping off the quck connect gasline, and there's residual gas dripping out from the bottom-under water somewhere.
Like I said before the other older rebuilt 1963 18 FastTwin motor seeps a bit of oil out of the drain holes which is nowhere near as evident when running it, the biggest issue here is the 72/58 FastTwin leaker motor has 4mph more top end power when running it, so I want to run this one as my boat is a 15 foot Alumacraft F9, and heavy.
Could this leak be the cause of the extra top end power?