2 stroke rebuild

[fishinut]

I am a 2 stroke fan, really enjoying this thread. You are being very meticulous, I like it. That motor got HOT, did a previous owner go cheap on oil or sloppy on the mix?

 

[79 Jimmy]

Thanks they sound great too

Cool thread Jimmy. Nice lookin alloy guitar bodies in the paint can shot too!

 

[79 Jimmy]

Thanks. I'm trying to build it better than the factory, my perfectionist tendencies are being put to use, How can you tell it got hot?

I am a 2 stroke fan, really enjoying this thread. You are being very meticulous, I like it. That motor got HOT, did a previous owner go cheap on oil or sloppy on the mix?

 

[fishinut]

The brownish discoloration on the cylinder walls and metal transfer on the thrust sides of the pistons are a dead give away. There is also carbon cooked onto the ports. A fuel pump failure or plugged water inlet would also result in overheating but I suspect lack of lubrication.

 

[79 Jimmy]

Good eye! Yes this thing got pretty hot at one point or two lol in its past. There is other evidence of it as well. If I had to guess I'd say there was a problem with the VRO. It's been running premix for a while....
Only 2 of the pistons where mangled though. 3 and 5, middle and bottom on the starboard side...

 

[Gunsmith]

Nice work thanks for sharing. Would love to hear the start-up that is the payback when you do this kind of project.

 

[79 Jimmy]

Sorry for the delay guys but life has been a bit chaotic lately. I'm glad I built this engine and fixed up the boat this winter while I still had money coming in on a regular basis. Recent events are going to provide me with more time than I thought to enjoy and use my boat this spring/summer. Anyway here are a few more pics of my progress.



First fire off!




Took it out on the river about a month ago for a little break in run. It was a little hard to start at first but after I figured out the starting sequence she likes it was easy. Just went on a little trip from Steveston to Wellington Point, opened it up a little more on the way back and realized it could use a little more prop than the 19" that is on it now. I think I'll keep it on for a bit just so I'm not pushing it while she breaking in but I'm looking for some suggestions for a new prop. I am leaning towards a 4 blade for an efficient cruise and to get on plane quickly but I'm all ears.....

 

[79 Jimmy]

Some video....

<iframe width="420" height="315" src="//www.youtube.com/embed/XQbs7GHQw4A" frameborder="0" allowfullscreen></iframe>

 

[profisher]

I had a 17 foot Double Eagle with a 115 Yamaha 2 stroke with a 17 pitch stainless prop. Over time I did start to get piston drop from worn wrist pins...a sign that I was running a bit to much prop. Personally I wouldn't go any higher in pitch. If your engine will slightly over rev at WOT that is better than under revs. Just never take it past he manufacturers max revs. By doing this you will be taking strain off the rotating assembly, especially when coming out of the hole.

 

[79 Jimmy]

Thanks pro, I was thinking about keeping the same pitch just going to a 4 blade in stainless. The 19" on there now is aluminum. I definately need to do a little more testing but I was quite happy with the performance especially from about 3700-5000. It would have gone higher but I didn't want to go above 5000 this soon. I hope my tach is accurate. Lol

 

[AquaDisiacIII]

Wicked thread! I did a similar project minus the detail on an '89 90hp evinrude 90 degree v4 that popped on one cylinder. Had the machine shop hone out the block and had to go .030 more on the bad cylinder. Had a great time rebuilding the thing but after looking at this I wish I spent the time to make it that clean. Nevertheless it was a great feeling running that thing for the first time let alone the first watertest. Great job!

 

[79 Jimmy]

Thanks AD3, I enjoyed the project for the most part. Painting isn't my favorite but it's all part of it. Definitely a sense of satisfaction it hear it light up! Still have to paint the engine cover, not sure I'll put stickers back on. I kinda like the stealth look. Lol. Or maybe a hash mark or small fish sticker for each caught fish like the fighter pilots put on their plane when they get a kill....