HELP...weird hesitation problem (UPDATED)

[CLL2437]

I was able to get my boat in the water yesterday and everything was going great until I ran into a problem. I was running the boat off and on for about 3 hours while I was fishing. I decided to try a new spot and headed that way I way turning about 4500-4800 RPMs. I started playing with the trim to get the boat to ride a little better and the RPMs went to about 5200-5300 everything was fine for a few minutes until the motor started to bog and I lost all power. I quickly got off the throttle and slowed down. Then motor still had no power and would run real rough in any RPM. I was cruising at 2000 and it was still rough so I tried to give it a little. The motor then acted like it was going to stall. I was in the channel so I and a long way from the marina so I pulled it over and fished for about 45 minutes. I knew I needed to get back so I fired it up and headed back. I kept it at 2000-2300 and it was running just fine. I went ahead and got it up to 4500-4800 and it was still running fine. I continued to fish and cruise around for another 3 hours keeping the RPMs under 5K and never had the same problem.

Does anyone know what could have happened? Were the RPMs too high? If it over heated would it cause this problem and was I suppose to hear a buzzer? I replaced the water pump and have run it with no problems before this.

BTW… The motor is a 1989 Yamaha 90.

Thanks,
Charles.

[Ken]

Charles,
Sure sounds like it is going into rpm reduction due to overheat condition, but you should hear the alarm buzzer going off also.
Test the alarm buzzer by disconnecting the two wires that lead to the thermo switch in the head assy. There should be two bullet connectors about four inches away from the thermo switch. Disconnect them, and with the ignition on, motor not running, short together the two wires that lead back to the ignition control. This should immediately sound the alarm. If it does not, then the alarm and/or associated wiring is bad.
If shorting the two wires does sound the alarm, then your outboard may be starving for fuel at high rpm. Check fuel filter and fuel pump per the Yamaha shop manual.
Good luck,
Ken K

[CLL2437]

Ken,

Thanks for the fast reply. I remember reading something about these motors going into rpm reduction. After reading your reply I drove to the storage and checked on the buzzer and thermostat. I found the thermo sensor and tested in like you said and it went off. I then unbolted the thermo cover and found there wasnt a thrermosat in there. I guess the guy I bought it from took it out. Would this cause the over heating and if so why didn't the buzzer sound?

[Ken]

Charles,
No, the absence of a thermostat would not cause the motor to overheat, but in cold weather, the motor might not get up to operating temp. A lot of boat owners down South here take out the thermostats - I prefer to use them so the outboard can get up to operating temp and run more efficiently.
From what you have said at this point, I would suspect a fuel starvation problem. The next time your motor bogs down after running at high rpm, check the primer bulb to see if it is still firm. If it has collapsed, then your fuel tank is not venting properly; or, if equipped, the anti-siphon valve could be sticking and not allowing enough fuel flow at high rpm. If it is still firm, go ahead and squeeze it a couple of times and see if your motor starts running smoothly again. If so, then a fuel pump would be suspect, or perhaps fuel filter or hose connections.
Good luck,
Ken K

[CLL2437]

Well, I bought a few parts that I needed to replace or add but it still didn’t fix my problem. I replaced the fuel pump and added a thermostat in the quest to track down the source of my hesitation. While I was out on the water I had the problem 4 times. I checked the things Ken told but no luck. I tested the buzzer and it works. The more I think about it the more I think it’s a fuel problem.

I took the boat out yesterday to a fishing spot 6 miles away from the boat ramp. I kept the RPMs around 3200-3500 with a GPS speed of 21-25 MPH. About 3 or 4 miles into the trip the motor started to bog and cut out. I cruised for a little bit at the 2200 RMPs unit I had to shut it down. After waiting for while is started it back up and make it to the fishing spot. I fished for a couple of hours and headed to another spot about 11 miles away. Again, I cruised at the 3200-3400 RPMs and made it there without any problems. I even got ****y and went WOT for a bit to see how fast it could go. I didn’t want to press my luck so I slowed it down. I fished there for an hour, moving from spot to spot (no problems) then headed back to the ramp. I made the 14 mile trip without any problems. Once I got back to the ramp my buddy wanted to hit a little spot close to the ramp. After we limited out I was so happy the hesitation was gone I started it up and went WOT in a hard left and the motor bogged down. I shut the motor off at decided to wait. I was drifting close to some rocks so I started it up to move a little. As I gave the motor the throttle I thought it was going to stay in the RPM reduction mode because it was less than 1 minute since it happened. I slowly sped up and found the motor was back to normal.

When the motor starts to hesitate/ bog I can feel it happening. It slowly started to slow down then finally gets down in the RPMs. If I have the control in the WOT position the motor will sputter. If I give only enough throttle to keep the boat moving it runs ok. If I try to give it a little more throttle it sounds like it wants to get going but then it starts to sputter.

Does anyone have any other ideas on what it might be? I talked to a Yamaha service guy and he stated he never heard of such a problem. I was thinking about rebuilding the carbs to see if that’s the problem. Is there any thing electrical I should be checking?

Thanks for your time guys.

-Charles.

[Ken]

Charles,
If it has been at least five years since last carb teardown and rebuild, I would do it. Reading back over your posts, problem could be gum/varnish deposits in carbs. A carb rebuild is due, and it just might fix your problem before you go looking at ignition.
Keep us posted,
Ken K

[bennymac]

I had the same problem with a 1988 200. I found the gas line and prime ball was the problem. Next time it stalls look at the prime ball.

[CLL2437]

Thanks benny. The last time it started to bog I run to the back of the boat and squeezed it. The bulb was hard and doing so had no effect on the motor. I bought a carb rebuild kit today and plan to rebuild them on Wednesday. I hop that fixes the problem. I was told to only run a Yamaha priming bulb so i might try that too. I think after I do the carbs I'll synchronize them and check the timing. I just don’t want to nickel and dime myself to death because I plan on looking for a 115 4 stroke soon.

[Ken]

Charles,
Let us know how you're carb rebuild comes out - carbs that are clogged with gum/varnish can give weird symptoms of motor performance - feedback from forum members helps all of us.
Good luck,
Ken K