Temp Alarm at Idle ? - The Hull Truth

fishin_Guy · 11-06-2008, 04:25 AM

This is my first time on your site, Everyone speaks very highly of you. Here is my issue. I have a 1998 Yamaha 150 carbed 2 stroke. The last few times I took it out the temp alarm has gone off after idleing a few minutes. It never has done that while running. I took the cowl off the last time and the starboard side cylinder head was hotter that the port side. Please tell me that I have not damaged the motor. I just replaced the thermostats in the spring along with the water pump. To my knowledge the poppit valve has not been replaced in my 5 years of ownership. I accidently started the motor dry a few times but only for seconds. Please let me know where to start. Where do I get the model number off the motor so I can order the parts.

bbogue · 11-06-2008, 05:02 AM

While you are waiting for Andy to respond, maybe I can help you with the location of model and serial numbers. On all my Yamahas, this information has been on a metal plate attached to the side of the gizmo that clamps the engine to the transom of the boat. Good luck. Andy is the best.

Bill

SIM · 11-06-2008, 07:11 AM

Quote:

fishin_Guy - 11/6/2008 5:25 AM This is my first time on your site, Everyone speaks very highly of you. Here is my issue. I have a 1998 Yamaha 150 carbed 2 stroke. The last few times I took it out the temp alarm has gone off after idleing a few minutes. It never has done that while running. I took the cowl off the last time and the starboard side cylinder head was hotter that the port side. Please tell me that I have not damaged the motor. I just replaced the thermostats in the spring along with the water pump. To my knowledge the poppit valve has not been replaced in my 5 years of ownership. I accidently started the motor dry a few times but only for seconds. Please let me know where to start. Where do I get the model number off the motor so I can order the parts.

Your engine model if it a 1998, would be a 150T"X"or "L" RW. The X and L depend on shaft length.

Um.....if the water pump and t-stats are new and working correctly, I would be leaning heavily towards the poppet valve beingstuck open. At idle speeds with the low water pressure, the cooling water is not making it up to the tops of the cylinder heads because that valve is open.

The parts are inexpensive.......getting to the area where the valve is at is harder. Get yourself a 10"-12" 1/4 drive extension, 1/4" drive ratchetand a swivel 1/4" drive 10mm socket. The poppet is located between the cylinder heads, at the aft end of the engine, down low in the lower cowling area........even lower then the lowest spark plug. There is a cover with a hose on it that has to be removed to get to it.

Shoot me an email if you are interested in a quote for the parts...... parts@shipyardisland.com . You can call too....1-800-213-3323 and ask for Andy Jr.

Andy

fishin_Guy · 11-07-2008, 04:50 AM

Thanks Andy. Will I know the part is bad when I remove it? Does this motor have a safety mechanism when it gets too hot? The starboard side cylinder head was considerable hotter than the port. I am concerned that it might have been damaged. What are your thoughts? Also, do you see thermostats go bad in 8 months?

SIM · 11-07-2008, 12:48 PM

Fishin,

The poppet does not normally go bad, but the spring that shuts itcan loose its stiffness and more then likely salt and crud debriscan keep the valve from shutting all the way. Yamaha changed the design of it so it is less likely to do that.

On the t-stats........normally no......they last longer then 8 months.

Andy

fishin_Guy · 11-08-2008, 12:36 PM

How in the world do I get the woodruff key out of the shaft? I tried a chisel, punch, hammer, vise grips. I am very reluctant to us a prpane torch because of the seals under the water pump. I put some penetrating oil on there with hopes it may loosen. Does anyone have any ideas? Any advise would be greatly appreciated.

SIM · 11-10-2008, 10:09 AM

Quote:

fishin_Guy - 11/8/2008 1:36 PM How in the world do I get the woodruff key out of the shaft? I tried a chisel, punch, hammer, vise grips. I am very reluctant to us a prpane torch because of the seals under the water pump. I put some penetrating oil on there with hopes it may loosen. Does anyone have any ideas? Any advise would be greatly appreciated.

We sometimes use a little heat on the backside key area of the drive shaft. NOT ON THE KEY.You are not getting it cherry red or anything even close to that. Just a little warmth to get things moving. I wish Yamaha re-designed the new pump drive keys with flat keys like Merc uses. Those literally just fall out.

When you do get it off, take the new key supplied in the kit to some Emory cloth or sand paper. You should be able to push the key in without smashing it in with a hammer You can use a hammer, but anymore then light taps is to tight for me.

Andy

fishin_Guy · 11-11-2008, 03:31 AM

It finally gave up and jumped out. Thanks to everyone for the help.