1987 Yamaha 200 overheat problem

bowhuntrrl

Petty Officer 1st Class
Joined
Mar 26, 2003
Messages
320
I've been trying to help my buddy cure his overheating problem that he's had for 2 years.The boat overheats (alarm) at idle, but alarm goes off after the revs are brought up a bit. I suggested that he buy a new poppet valve and seat and spring. He also bought a new impeller kit for the water pump. The poppet was not at all like the old one, it looked like a mushroom with a rounded head. The seat they gave him was just like the old one, and they didn't give him a new spring, so he used the old one. He also did the water pump impeller. Less than a minute after starting, the alarm went off and heads were hot. He took the lower end down and checked the water pump. He did this 3 different times, and still had the problem. At this point, he asked me to check his work. We dropped the lower and took the water pump apart. I didn't really see a problem, so I reassembled it. The only thing I did different was to torque the cover bolts to 5 ft lbs, instead of the extra tight that he gronked the bolts down to.I then checked the poppet valve. I couldn't see how the button head of the valve could seal the flat surface of the seat, so I put the old poppet back in. We fired it up, and the problem seems to be gone. Only problem is, I don't know what fixed it. My question is: Does the new style poppet require a different seat and spring ?? I'm leaning towards a water pump problem because the telltale stream was much stronger after I put the water pump together. Could he have tightened it enough to distort the plate or something similar ?? I'm real curious about that new style poppet valve though, since that's the only thing that we really changed. When we took the poppet apart the first time, it was assembled backwards and stuck in the seat. Could that have been the original overheat at idle problem ?? Thanks.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1987 Yamaha 200 overheat problem

most likly. if the poppet is not sealing it will dump he water pressure and the block wont fill and #1 cyl gets hot. the other suspect area is the rubber dam and holder at the fwd egdge of the ex cavity that the aft end of the wear plate sits on. occasionally corrosion will lift it slightly and the new pump wont seal.<br />but removing and cleaning it is part of the pump job.right?
 

Ray Neudecker

Lieutenant Commander
Joined
May 25, 2004
Messages
1,656
Re: 1987 Yamaha 200 overheat problem

Seems like you fixed two problems. Overtightning the pump housing can cause it not to seal properly. A poppet valve problem will show up quickly at idle.
 

bowhuntrrl

Petty Officer 1st Class
Joined
Mar 26, 2003
Messages
320
Re: 1987 Yamaha 200 overheat problem

Anyone familiar with the "new" style poppet valve that the dealer gave him ?? It had a mushroom shaped head and a short stem for the spring to fit over. They gave him a seat that looked just like the old style. This makes no sense to me, round surface against flat seat ???
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1987 Yamaha 200 overheat problem

it works, sticks less too,for those that detest periodic maint.
 
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