2001 Yamaha 150 will not stay running...help

[Kprmbrjpr]

Hi all,
I have a Yamaha 150 2 stroke. For the past few months the engine would bog down when run at high rpm's. I figured the carbs needed to be cleaned, but just never got around to it. I tried to start it a couple days ago and nothing. I get it to turn over but only after I've choked it a few times and have the throttle down about half way. It will run rough for a bit then slowly die. I took the carbs off, cleaned (were not bad ) and rebuilt with new gaskets. I changed the battery, checked the spark plugs. Changed the fuel pumps, the primer ball gets nice a tight. I took the fuel filter off and found a small amount of water. I do not have a water separator, but the amount of water was very small and have never had a problem with it before. I tried to start it on a remote gas tank thinking the problem could be with the boats gas tank, but got the same results. I'm all out of ideas, any help would be greatly appreciated, thanks.

[99yam40]

check compression , spark, and timing to start out with to make sure those are good

[Kprmbrjpr]

I checked the spark, it was all good. While taking out the plugs, a few beads of water were on all six of them. I'm not mechanic, but I know this can't be good. Anyone know what could cause this?

[YammyMan]

I would do as 99yam40 guy says. Check compression. But it sounds like you have a blown head gasket. Worse case cenario, busted block. But sounds like a blown head gasket. Is this a motor used primarily in saltwater? Did you completly disassemble the carbs, soak them over night, and then blown them out with compressed air?

[damirdaco]

clean better that carbs, disassemble the whole parts of it..

[jb123]

if you see water, check separator and motor filter, then if ok, pull head
no separator... bad

[dwarren77]

It does sound like your carbs need to be taken apart and cleaned. If you are using E10 gas then I would start with a complete cleaning of the carbs first. You can use a compression gage to check the head gasket but I leaning towards your first thought.

[Kprmbrjpr]

Thanks for everyone's help. I did take the carbs out, disassemble, clean and rebuild with all new gaskets. I just ordered a compression gauge. As soon as it gets here I'll check that. After all the research I've done, I'm leaning toward a blown head gasket.

[99yam40]

If you have water inside that motor there will be rust forming in places that are not good

[Sequoiha]

in this case i would do a leak down test,,