150 SS overheat alarm issue

[Mike O]

I have twin Yamaha 150 1998 (mfg. 06/97) Saltwater Series (carbs) on my 27' walkaround. They have performed well although I do not put a lot of time on them. A few months ago apparently after a routine replacement of water pump impellers (by a Yamaha certified mechanic) the port engine began giving overheating alarms and shutdowns after 3 or 4 minutes of 4000 or more RPM. We reversed the sensors and the problem persisted on the port (same) engine. Since then we have replaced the sensors, thermostats and impeller housings. The problem still persists and now will alarm at sustained RPMs as low as 3600. In all cases we immediately used a remote, external temp sensor on the motor and all readings appear to be normal. The starboard engine has had a similar alarm and interruption at least once.

[jb123]

i have twin 200`s and yesterday had a alarm go off and i have all new parts. sometimes you will get overheat signals as yammies do not like any interrption of waterflow. i was just idling after a hard 20 min run....turned it off for 1 min,restarted and all better. if you havent replaced your prv pars, go ahead as theyre quite cheap.

[Mike O]

Thanks,

I restart and when get up to speed the alarm goes off again.

What are prv par(t)s?

[slim]

prv=pressure relief valve. located on the back of the powerhead at the bottom. you can clean it of corrosion and stretch the spring just a little. the plunger should slide easily in the rubber grommet in the block. if not, remove the grommet and clean hole.

[Ken]

Mike,
That prv, aka pcv (pressure control valve), aka "poppit valve", is designed to open at around 20 psi to relief over pressure in the water jacket/cooling system.
Debris can get stuck under the valve/seat and keep the pcv from closing completely. When this happens, cooling water from the water pump will pre-maturely dump out the relief holes. This will also shoot the heck out of your water pressure , and cause overheating/alarm.
You would be wise to go ahead and replace the pcv with the new "mushroom" design that is less prone to sticking open - I think it is less than $10.
Good luck [img]smile.gif[/img] ,
Ken K