8.0 HP Yachttwin 1995 Two Stroke Rebuild

[carboman]

I have a 8.0 HP Yachttwin 1995 Two Stroke that runs decent. I know I have some minor scroing on the bottom cylinder. It more resembles a smooth, dark gray streak the length of the cylinder stroke and about 1/4 inch wide. The motor runs decent, but I think I am getting some blowby resulting in exhaust coming back into the air intake area which shows itself as exhaust comming out the front of the enginer cover by the tiller when running.

I want to do a rebuild, but not sure what I will need. I am hpoing the pistons are ok.

I am thinking a cylinder hone, new rings, rod and crank bearings at the least.

Any suggestions are greatly appreciated!

Dave

 

[iwombat]

Re: 8.0 HP Yachttwin 1995 Two Stroke Rebuild

If your scoring is deep enough that you're getting _significant_ blow-by you'll need to go to a set of oversized pistons. You'll be taking the whole thing apart to do the job anyway, so why waste your time on a gamble? Take the block to a machinist that specializes in marine motors and see what they say.

 

[raczekp1]

Re: 8.0 HP Yachttwin 1995 Two Stroke Rebuild

but if exhouste is comiong from under cowl you need to change a gasket between powerhead and midsection.its all.

to check how helth is your cylinder.pistons is to do compresion test for each cylinder.3 puls for one hole and 3 for the next with odcourse kill buton activated

sometimes pistons are scored or run out necouse overhiting or bad oil.
i would unscreav powerhead side panel and look at pistons first.
mostly cylinders are ok but you need neww pistons and rings, standard ones.
if you order pistons assemley kit you get nistons, rings and whirst pins for one.
just order 2x pisston assembly

 

[nwcove]

Re: 8.0 HP Yachttwin 1995 Two Stroke Rebuild

i agree with racz, do a compressin test before you do anything else. post back with the results. if comp is ok, you just may need the power head to base gasket to stop the smoke issue. even put your hand around the exhaust plate with the motor running to see if its leaking there, if it is, its no problem to feel it.

 

[carboman]

Re: 8.0 HP Yachttwin 1995 Two Stroke Rebuild

Thanks for all the feedback! I will do a compression test this weekend. I did one last year but can't remember what the results were. I know the bottom cylinder was lower, the one with the scoring.

I did replace the gaskets that go between the power haed base, the plate and the bottom hoousing. I had to replace the watter intake copper tube since it was corroded into the lower unit. That part went well.

Thanks!

Dave

 

[nwcove]

Re: 8.0 HP Yachttwin 1995 Two Stroke Rebuild

how bout the exhaust plate gasket, on one side of the powerhead? (should be a discolored plate from exhaust heat).