3.0 Merc hit 230 degs!

[Wellcrafty]

While motoring yesterday in some fierce wind/waves with 4 heavy peeps on board with the bimini up, the temp gauge went to 230 before I noticed. It had never did this before on my 89 wellcraft 170 with 3.0 mercruiser, alpha1 drive.
I backed it way down from the 3 grand rpms I was doing, and it cooled down to 170 or so. Ran cool the rest of the way into the harbor. We moored, I dbl checked the lower unit, etc. I noticed some weed build up, but nothing major at all. I cleared that away regardless. We sat for over an hour, then fired it back up, it ran well afterwards. Ran nice and cool (140-160) and I even pushed it to 4 grand on the tach heading back to the launch. It never got hot again. What the heck??? Racking my brains trying to figure this one out. The impeller was replaced 2 yrs ago, plus it ran cool coming back. I wonder, was it clogged by weeds and couldn't suck in enough cooling water? Did I hurt something by hitting 230 before getting it cooled back down?? I am noticing a slight vibration in the drive now at low rpm's, after backing it back down from higher rpm's. Never noticed that before.
Any idears friends??

 

[Wellcrafty]

Re: 3.0 Merc hit 230 degs!

I can't believe nobody had an idea about my issue... WOW!

 

[dodgezilla04]

Re: 3.0 Merc hit 230 degs!

possibly the suction came out of the water briefly in the waves and sucked air? the pump would eventually reprime

 

[Howard Sterndrive]

Re: 3.0 Merc hit 230 degs!

 

[bigskiohio]

Re: 3.0 Merc hit 230 degs!

without warnings i watch my gauges constantly,they sell buzzer kits.

 

[Don S]

Re: 3.0 Merc hit 230 degs!

That would be my guess as well. It's killed many an engine.
Next time you get an oveheat like that. Idle down, then shut the engine off. If that plastic bag is over the pickups, the suction from the pump will hold it on. If you have just sea weed, usually reverse will get it off.
As far as 230? goes, that's hot, but not enough to do damage to any engine parts. The worst problem would be burned exhaust hoses and possibly damaged impellers from lack of water.
When you hit 260 and above is when you can start doing damage to things.

 

[myoldboat2]

Re: 3.0 Merc hit 230 degs!

the bag sounds right, but i'll share what happened to me. i had occasional overheating about 6 years ago. no reason i could see, just every once in a while at higher rpms the engine would overheat. i eventually tore down as much of the cooling system as i could... manifold ok, top elbow ok, bellows ok, replaced the shutter, lower elbow ok, replaced the outer bellows, changed the raw water pump once again. still overheated once in a while, like once every third outing. i pulled the gear housing off the drive shaft housing and traced the cooling path. my older drive has the water pocket. there were some old small bits of impeller in there. at high enough rpm (raw water flow), the turbulence in the water pocket would sometimes raise pieces high enough to plug the outlet port of the water pocket. it took me a while to find it, but it solved the problem. without a water pocket, i don't know if old impeller bits can hide in the cooling circuit or not.