1993 Yamaha 225 overheating

[h2orampage]

I have a 1993 225 Yamaha (mod. No. 225 TX RR) on a 24 Proline WAC that I have owned the past 12 years. Recently, the engine overheat buzzer and automatic rpm reduction engaged within 30 seconds of getting boat on plane. Within one minute, overheat buzzer shuts off and I can idle at up to about 1500 rpm without the overheat buzzer engaging. I changed the water pump yesterday and thought that was the problem when I found the large o-ring to the pump housing split. Today I ran it and the same problem occurred...overheat buzzer and rpm reduction within 30 seconds of running. I change the water pump annually and last year changed the thermostats and popet valve (first time that I recall). I always flush the engine after every use. Engine's been running great until last week. Tested compression and checked plugs and both are good. Heading to the keys in 2-1/2 weeks for some lobstering and fishing and need to get problem fixed ASAP. Any ideas? - maybe bad or clogged thermostats or popet valve? Your assistance will be appreciated.

 

[rodbolt]

Re: 1993 Yamaha 225 overheating

are you positive its an overheat?
the horn tone is the same for low engine tank level,low battery voltage and a few other alarm conditions.
the visual indicates on the tach or speedo will tell you which is the alarm condition.
a clogged remote tank oil filter can give the same symptoms.

 

[h2orampage]

Re: 1993 Yamaha 225 overheating

Yes - very familiar with the different warning lights (e.g., low oil). This is definitely the overheat light. Since last posting, pulled thermostats and popet. Left thermostat & housing have a lot of salt buildup vs. right side. Popet looks good. I am concerned there may by some water restriction somewhere in the water jackets... engine is 16 years old (1500 hrs).

 

[Scrapiron]

Re: 1993 Yamaha 225 overheating

Hi, I recently bought an '87 yamaha 200hp. Was having an overheating problem as well. I was told to check the PCV grommet as well. As it turns out the port side thermostat was sticking on mine. I went ahead and pulled the heads anyhow and cleaned all of the water jackets. This process only took a couple hours. As my motor is 22 yrs old.....its been through alot of water pumps, and as far as i can tell, heads have never been off. I cleaned all the small pieces of rubber from the jackets, then blew all of them out w/ my air compressor and then ran a waterhose through them. Put it all back together yesterday and all's well. New water pump,cleaned jackets, new thermos, checked PCV grommet, and now i'm good to go. Off topic(also rebuilt the carbs as it had been sitting up.) Going to the lake this afternoon, ran like a top w/ muffs on. Keeping my fingers crossed, this is my first boat, and first time out WISH ME LUCK!

-Scrap

 

[h2orampage]

Re: 1993 Yamaha 225 overheating

After changing water pump/impeller and cleaning thermostats and popet valve, I ended up pulling off and cleaning waterjackets as well. Took out and within 2 minutes, same overheat warning occurred. Checked actual temperature of cylinder heads using a $10 infrared temperature gauge bought from Harbor Freight. Temperature in all cylinders was fine so it wasn't actually overheating. While the overheat alarm was going off, the cowling was removed and we disconnected the 2 wires to the overheat sensors one at a time to determine which side was being being tripped (located on the top cylinder of each side). Voila! Disconnecting the top left sensor stopped warning buzzer. Ran boat again without sensor engaged and it ran great. Double checked temperature again using infrared gauge - perfect! Long story short... Problem was simply a bad heat sensor that was signaling overheat problem when there really was none. Replaced heat sensor for $35 and everything seems good now! TIP - buy a $10 infrared gauge to keep on your boat. If ever out on the water and overheat alarm goes off but water seems to be pumping out of pee hole good, check temperature of heads using infrared gauge to determine if actually overheating. If not, you may be able to disconnect heat sensor(s) as I did and continue operating. However, be sure there is no overheating before doing so.