View Full Version : Overheating Yamaha 75

06-16-2003, 08:24 AM
" My yam AET75 (2 stroke, 3 cylinder, 3 carb, 3 coil) - I think is around 1988?
Ran perfect last year but it's first run this year the water turned to a trickle, then none from the telltale, but water was leaking from the front of the motor (top of the leg) where the motor pivots on the bracket.
It overheated and I thought it would be the impeller but after removing the lower unit the impeller still squeaks when you turn the shaft and feels like it still works.

I notice that the place where the water was appearing there is a rubber part that was a bit wobbly when prodded as if it is maybe a gasket or seal (about say 4-5mm thick) that has broken/shrunk etc?
This has never had a problem before so why would it suddenly be ruined?
Any advice would be much appreciated, especially on what is required to replace this part (removal of powerhead?!) or what the part is called & is for.

Thanks very much! "

06-16-2003, 06:43 PM
" Jim,

The water leak that you saw might mean that the gasket at the base of the powerhead is bad. That could cause water and exhaust to mix.

By the way, you can view a parts manual at the Yamaha website now. I think you need just the model number.

Tony "

07-06-2003, 07:03 PM
" Thanks for the reply Tony.

I attached the engine to a hose yesterday and ran it and water really started blasting out of the tell tale to my delight!

There wasn't any appearing elsewhere either and the rubber seal I was looking at is just a seal between the leg and the casing that goes round/beneath the powerhead - don't think it's really a functional part so to speak.

Anyway I ran the motor for a good few minutes with the hose on it to see if the water stopped coming from the tell tale again but it carried on firing it out. There's still something funny going on though as the overheat buzzer started going off even though there was water blasting out the telltale and some coming out through the prop. The water from the telltale was pretty warm but not boiling how at all, so is it possible that the alarm is just being dodgy?

I can't see that the engine can really be overheating when there now seems to be plenty of water coming through it again. Any ideas?!

By the way - do you have a link for the manuals on the site? I had a look but can't find them so I guess I must be looking at the wrong site or something? "

07-07-2003, 05:35 PM
" Well, I solved the problem today. I removed the thermostat housing and was simply shocked at the amount of crap in there!! Sand, grit, salt crystals and muck had just about completely blocked the waterways up and had filled up the thermostat.
I removed all the bits round the thermostat, cleaned them and scooped all the crud out of the housing, then reassembled it and fired the engine up on the hose again.

Hey presto - no overheating. She ran like a dream!! I'm delighted to have saved myself a load of mechanics fees and that my baby is good to hit the high seas again. :o) "