Alarm sounds when going above 2/3 throttle

[Dingopointer]

I have Yamaha outboard C150TLRU I think it is either 96 or 97 (the boat it came on is 97).

It starts great and runs well and even until I reach 2/3 throttle. Then above that it runs for about 2-3minutes then alarm sounds and the engine looses power. The alarm tone is long uninterrupted. If I switch the engine off and switch back on immediately - the alarm persists. If I switch off and switch back on in about 30 sec or more - it runs same as before (great until 2/3 throttle.

Please - any ideas would help.

Damir

P.S. This engine requires fuel and oil to be premixed. So no oil tanks, injections etc...

 

[rodbolt]

Re: Alarm sounds when going above 2/3 throttle

carefully test the temp switchs as per the manual in a pan of water with a candy thermometer.
if the temp switches are ok, bad news.
if they are ok it means pulling the water jacket covers and cylinder heads and manually scraping the scale off the metal water passages.
suxs but it happens.

 

[Dingopointer]

Re: Alarm sounds when going above 2/3 throttle

Unfortunately I do not have the manual for this motor. Do you know of any place on the web where the procedure is described? The one for testing the temp switches?

Thanks

Damir

 

[objm]

Re: Alarm sounds when going above 2/3 throttle

The same thing was happening on my 200hp Suzuki. Come to find out it was getting hot because the thermostats where stuck closed. Took them out and everything is go... dont need them anyway...

 

[Dingopointer]

Re: Alarm sounds when going above 2/3 throttle

If the engine was overheating - would it be hot on touch inside? I mean - it is warm but not very much at all. Also the water shooting out of the engine stays just a bit warmer than water outside the boat. Also if it would get overheated can it cool off so fast? 10-20 seconds after stopping it - it continues operating fine. It will run great all day long unless I bring the throttle past 2/3 way down. Then it runs for 5 min and zoom comes back again. Turn it off - count to 20 and it is ready to go again.

I am not disputing what you have said earlier just hope more details would give you more ideas. I really hope I can avoid taking it to Yamaha dealer (I NEVER have taken my boat anywhere and not end up paying in excess of $300...