2 stroke to 4 stroke

[DennisG01]

This rig does not have a tac. One is on order. 3/4 throttle is about an inch away from full. If I push it that far she stalls

OK, that's a totally different scenario. I don't think compression is going to be causing your issue. Low compression just wouldn't have enough power... sort of like: Whatever "power" you had at 3/4 throttle would be it... advancing the throttle further wouldn't yield any more power. I don't know a whole lot about timing, but it sounds like that's the direction you want to head - have a tech look at it and check timing for WOT. May just need a tune up.

[DennisG01]

I dont mo d the 15 mph. Just do not want to move slower if I go with the 4 stroke. Keep hearing 2 strokes are faster. But hoping to resurrect this one

Old thinking. The power "comes on" quicker, as a general rule, with 2-strokes (given the nature of how they produce power in 2 strokes as opposed to taking 4 strokes to do it). But the final power is the same - or close enough as makes no difference. Newer 4 strokes are pretty darn close in the "comes on" category, as well.

[Tsgtwheeler]

Ok thanks for all the help

[Tsgtwheeler]

At lunch there was no change. I did however add a little bit of 2 stroke oil and the compression check went up to 120. Now I lofted it up and added a teaspoon of ring free. Will let it sit

[Tsgtwheeler]

That didn't do anything. I added 6 oz of ring free in 3/4 gal of mixed gas. Let it run for 15 and then let it set for about 45 min. The let it idle at high idle until the rest was gone and went up to like 93 psi

[Tsgtwheeler]

Guess I can just run this on until it breaks while saving for another outboard. I have tried all I know and all yall say to do. I called a dealer and asked for a rebuild kit and they said the 2 cylinder models are obsolete and no kits.

[DennisG01]

I have tried all I know and all yall say to do.

You already had a tech look at it? Specifically the carbs? What did he say about it?

The 90-ish psi is not the problem.

Hindsight is 20/20, but... ALWAYS check things out BEFORE you buy. If you had, you could have worked this out through negotiation. Chalk it up to a learning experience.

[Tsgtwheeler]

Yep she runs good ran carbs through a deep clean. I haven't put it in the water since I found the 99 psi. I thought that was a big problem the other cylinder is at 120

[DennisG01]

Yep she runs good ran carbs through a deep clean. I haven't put it in the water since I found the 99 psi. I thought that was a big problem the other cylinder is at 120

But simply cleaning them doesn't mean they are operating correctly. They need to be "tuned", so to say. It's not something I can advise on HOW to do it... just that I think it's sounds like something to pursue.

It's not clear... did you actually have a mechanic look at the carbs in terms of adjustment (and I suppose throttle linkages, etc)?

[99yam40]

on that old 2 cylinder motor, is it the cylinder that runs the fuel pump the one that has low compression?
if it is have you made sure the pump is not leaking into the crankcase washing the oil off of the cylinder walls and piston?

I am guessing this is an oil injected motor and not a premix

[Tsgtwheeler]

This is a premixed. I have not had a tech look at it. I have worked on cars a long time. But if it was a car I would have rebuilt it already. When the weather gets better I will take it to the lake. I like to adjust with a load on it. I have talked to the yamaha tech he told me since the lower cylinder is at 90 I need a new powerhead. Since the upper cylinder is 30 psi higher. He said they do not have kits for the 2 cylinder outboards. And I needed a outboard under 215lbs to keep weight ratio the same

[Tsgtwheeler]

Ok thanks for the info

[Tsgtwheeler]

My motor was not listed c40plrr

[Tsgtwheeler]

Oh I found it it's a 93 not 92

[panasonic]

I would buy a cheap scope and have a look in that cylinder to see if it is scored up before doing anything else.