Help with my 1989 150 Yamaha 2 stroke!

[InshoreEd]

I bought a b 19 flats boat with a 1989 150 2 stroke about 2 months ago.

Engine looks to be in great shape and ran great for 2 months. 2 weeks ago it started acting a little funny. Once the motor warms up now (after running about 15mins) it seems to go into gardian mode (I think thats what you call it) the motor will run at 1500rpms but if you push it to 2000 (Wont go more) motor feels like it will vibrate off the transom.

At first it seemed like a fuel restriction issue. Broke down and rebuilt carbs. That wasn't it. Changed out the 2 fuel pumps and of course changed out fuel filter and in line filter H2O Sep. That wasnt it.

I had a few buddies that are Yamaha mechanics (but work mostly on 4 strokes) look at it a few days ago and they were sure it was electrical. Tested the Stator and the high rpm value was only 20 and so replaced the Stator today (expensive) and at sea trial it ran better but after 15mins same thing.
Plugs seem to be burning a little wet.
Compression is 110 every cyl except 1 which reads 108..

When the problem happens and you turn off the motor and restart you can run 5-10 min before it happens again.

The oil pump was taken off (before i got it) and the valve was rigged so not to indicate low oil. I don't think this is the best way to go premix but I also don't think thats the prob.

At one point I thought it was overheating (replaced the water pump) and ran it with out the cowlin on a flat day this week. Same prob. engine was not to hot could put my hand on it for a good 2-3 min no prob. Thought maybe the alarm was bad...but that's not it.

I haven't checked the gas tank as it's glassed in on my boat but I guess my next step is to run it with a 5 gal gas can and see.

ANY HELP WOULD BE MUCH APPRECIATED.

 

[will941s]

Re: Help with my 1989 150 Yamaha 2 stroke!

I also have a 89' Yamaha 150 and the problem I have sounds pretty close to yours. The only thing about mine was, from the get go it would'nt get over 2,100 rpm's. It would surge a little and hit 2,800 but mainly 2,100 was the max. I took it to my mechanic and after all the tests came back it came out to be a fuel problem. He replaced the fuel system from the engine connection to the carbs. He was going to clean and re-seal the carbs but he had to completly rebuild them due to the Ethanol on the gas that pretty much ate them up. All the jets were clogged. The total job costed $588. I hope this can help you out.

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Thanks Will. I guess misery loves company....right?

I cant figure it out and its really frustrating me. I was sure it was electrical after they checked the Stator but no luck there.

Anybody else have this type of problem?

Do these motors have a safety mode? What I call the "get to home port with out screwing up your motor" mode?

Any help would be apprec. I've had 3 mechanics look at it but times are tough and Im trying to do the work myself. Pretty mechanically inclined but not with this motor!

Anybody?

 

[cousinabe]

Re: Help with my 1989 150 Yamaha 2 stroke!

The motor is going into reduction mode to protect itself from damage.
Do you have yamaha gauges, are any indicators flashing on the gauge?

Things that cause the motor to go in to reduction mode are:
1) bad battery connection. check all grounds and cables.
2) overheat condition
3) low oil alarm
4) remote oil transfer alarm. usually a clogged external filter on remote oil tank or bad switch.

If you don't have yami gauges:
When it goes into reduction mode, is the engine warm or too hot to touch? this would indicate overheat.
how much oil is in the engine mounted oil tank when it's vibrating? if it's way low, this would indicate oil transfer problem.

 

[David Greer]

Re: Help with my 1989 150 Yamaha 2 stroke!

I hope it's carbs but it sounds like could be this: Previous owner ran it without oil/water, and the head or other parts overheated--not enough to lock up or whatever real bad, but slightly. Now when the parts get heated--not over-heated--the warpage is intensified and parts that should run smooth are twisted and bouncing around in there. If you promise not to say "what did you do that for" here's why I think that: "we" ran a 70 hp OMC without oil (either the tank went dry or the hose came undone and the alarm failed) and the engine wound down and quit. Restarted after adding oil and it seemed to run OK for a few minutes and then did it again: ran down, as if it were running out of gas. Same deal the next day so we towed it; my mechanic told me the above scenario. I also had a water pump fail on a 196? 18 hp; it clanged around so I shut it off; restarted a while later and it ran OK for a while and then did it again. It was later I suspected the waer pump (no pisser back then).
It's the fact that you just bought this that makes me suspect damage you don't know about. Can you interrogate an trust the previous owner and is he knowledgeable?

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Thanks gentleman,

I know its not going into reduction because of overheating....ran w/o the cowling and normal op temps.

I will check all grounds and connections and let you know what I find. I didn't really think of that.

The motor was converted to premix and I checked the sensor (rigged not to go off and working). I ruled this out but will give it another look.

Thanks for the help

Can you confirm they are the only 3 things that send the motor into reduction.

Cheers and keep you posted

 

[cousinabe]

Re: Help with my 1989 150 Yamaha 2 stroke!

yes. oil or overheat.
do you have yami gauges?

even though the cowling was off, did you physically touch the power head?
possibly a bad thermo switch??

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Also, When I purchased the boat 2 months ago the motor ran incredibly well! That's one reason I bought it. It ran great for a month and a half (and I fish it 3-4 times a week. It really think its something trivial... compressions great... good spark .....carbs didn't even look that bad when I pulled them.
The plugs are burning a little wet now since this started.
I've spoken to the previous owner and I believe it to be a solid unit. A few mechanics have looked at it when I pulled the carbs and they agreed it super clean and shows no damage whatsoever....I'm also very optimistic David!

Any chance this could have anything to do with the thermo switch? I know nothing about them but it only happens when the motor warms up. Isnt that a switch activated by heat transfer?

Thanks for the help fellas

 

[cousinabe]

Re: Help with my 1989 150 Yamaha 2 stroke!

while the alarm is sounding disconnect the pink wires at the heads. this will eliminate the thermo sender switches.

you can test the sensors in a pot of water with an ohmeter and a candy thermometer. switch should close about 190 degrees

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Cousinabe

Thanks, I did check powerhead with my hand warm but not to hot 30 secs or so. Actually cooler than I expected.

I'm not sure what the thermo switch does or how it works. Can you test it?

Thanks

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Thanks Cousinabe You read my mind.

I'll check it and let you know

Thanks for the ideas and advice

 

[cousinabe]

Re: Help with my 1989 150 Yamaha 2 stroke!

i think we are both posting at the same time... read my post above.

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Sorry about that....It's my first time posting on here

Great forum

Let you know how it works out thanks for the help

 

[InshoreEd]

Re: Help with my 1989 150 Yamaha 2 stroke!

Thanks so much for the help. I went trough everything and the culprit was the thermo switch. The alarm on the motor also went out at the same time this was happening by coincidence and so it was more difficult to detect. Repalaced both and running much better.

Thanks all again for the assistance.

 

[David Greer]

Re: Help with my 1989 150 Yamaha 2 stroke!

typical boat problem--two simultaneous but non-apparent problems preventing trouble-shooting! BTW I re-read your first post and since you ran OK for a while my theory doesn't work. Good that you had access to previous owner, too. That always helps.

 

[cousinabe]

Re: Help with my 1989 150 Yamaha 2 stroke!

Ed, glad you got it sorted out.... as far as problems to have, those ain't that bad!