30hp Yamaha overheating buzzer???

muskiekid · #1 April 29th, 2003, 07:41 AM

First off, I would like to say that this is an awesome board... One of the most active sites I've come across.

I need your guys help. I took my boat out equipped with a 96' 30HP yamaha out for the first time since it returned home from winter storage. I fire it up and it starts easily but when I give it 3/4 throttle or more, it overheats... or at least the buzzer goes off. I can drive it for a good 20 minutes or more at half throttle or less but when I give it more gas, it overheats. I had a similar problem (but different) with it last year but it would drive for 15 minutes at full throttle before hearing the overheating buzzer. And then I had to wait til' it cooled down before I could turn the key without hearing the buzzer. I had it serviced at my local marina and the problem was fixed with a new impeller. Now comes the weird part...

Knowing I had a problem with my outboard and still wanting to fish, I decided to just use the trolling motor. 15 minutes into fishign with the trolling motor and with the outboard off, the buzzer goes off again. I had to turn the key another click to where it allows the key to come out. Why would the buzzer go off with the motor off? Do you think it could be the impeller again or something else? I purchased a manual for my outboard so maybe I could turn a few wrenches and check out some stuff.

I also checked the oil level and it was fine. Can someone point me in the right direction?

Thanks in advanced.

Kirk

muskiekid · #2 April 29th, 2003, 07:44 AM

I would also like to add to the above. When the buzzer goes off, I can just turn the boat off and then back on again without waiting and I can drive around at half throttle.

Thanks.

skiffer · #3 April 29th, 2003, 08:12 AM

When you shut the motor off the cooling stops so the stored heat in the cylinders conducts out to the region around the thermostat and sets it off again. I had a Faryman diesel once that did the same thing. If it was hot and I turned it off, I couldn't turn it over again for 1/2 hour or so untill it cooled down.

muskiekid · #4 April 29th, 2003, 01:36 PM

Thanks for your reply skiffer. The problem that I am having is a little different than what you explained... actually you answered the question in the second paragraph but what about the first paragraph. I was able to drive at half throttle but the very second I gave it more gas, the buzzer would go off. All I had to do is turn the outboard off for one second and then I could restart it and continue going again at half throttle. The overheating problem I had last year was different, I had to wait for it to cool down before I could restart it.

Any more suggestions? Thanks again.

Kirk

redyute · #5 April 30th, 2003, 07:52 AM

i'm not sure if you could perform this test but if you can,run a test on the thermo sensor.Take it off put it in a pan with water and let it heat up.Use a digital meter on the wireing to see if you get continuity when the water heats up not when it is cold.If you get continuity when cold then you have a faulty switch

jim dozier · #6 April 30th, 2003, 08:23 AM

First see if you can determine whether or not the engine is actually overheating. Does the motor put out a good pee stream? Can you keep your hand on the block between the flywheel and the cylinder head (be careful of the spinning flywheel) at full throttle for at least 5 seconds. Or better yet get the heat sensitive crayons from a dealer and check the temp of the block that way. If it isn't overheating you probably need a new sensor. I have a Suzuki DT85 that was doing something similar. It was overheating, but after I had done a consideable amount of work to fix the cooling system the buzzer would still go off occaisionally. I called the dealer and got the temp range of the sensor and found that my sensor was or had become too sensitive and a new sensor ultimately was required to shut the buzzer up. It is difficult to test the sensor because mine is in contact with the head not the water and is supposed to go off at 237 F. Water boils at 212 F and won't get hot enough so you would need to heat it up accurately and record the temp another way.

If the engine is overheating, start with a new impeller and housing and check the thermostat. Thermostats can be checked with a cooking thermometer in a pan of boiling water.

muskiekid · #7 May 1st, 2003, 07:41 AM

Thanks for the replys guys. Its nice to see you can get good help from around the world via the Internet. I've printed this section out and will pop the hood tonight after work. I'm not that technical when it comes to outboards but my friend is a car mechanic and with the use of this thread and the manual, I think we might have a chance to fix this problem. I'll keep you guys informed with what happens and if you guys or anyone else has any more suggestions... keep'm coming.

Thanks.

Kirk