engines HOT

apdcop

I am just curious if this has happen to anyone else.  I was out a few weeks back and my starboard engine got to temp of 240 and alarm came on.  I shut it down right away.  

I had both impellers replace last year, so I am fairly certain that it will not be this.  

Today I ran the engines at idle for at least an hour while sitting at the dock.  The temp never got above 180 on either engine.  I also even throttled them up to around 1800RPM just to see if the temp would rise.  (it didn't rise at all)

Someone told me that the mercruiser's also pick up water somewhere on the out drives (I've have never heard this).  So  curious does any one knows if the are another set of impellers on the out drives?  Or does anyone know where I can start to trouble shoot this problem?

Thanks in advance.

PATRICK MAGRUM
   

LaRea

Bravo 3 outdrives have a pickup in the drive, but no impeller.  I think the Alpha has an impeller in the drive.

Do a search for "Bravoitus" ... you might have a restriction in the hose fitting that comes from the drive up through the transom to the engine.  

rasbury

I have the bravo 3 on my 270. You have a pump on the motor belt driven that pulls water through the out drive.  @LaRea is spot on but there is no way to check that- at least without pulling the drive- I had my motor out and replaced that connection- not sure if you can do that from the drive side or not. I also have a thru hull so I pull water through that also. If you have a sea strainer with a hose to the water pump make sure that thru hull is open and the strainer is not crudded up- if the impellers were bad it would heat right up at idle. If you are closed cooling, you have a heat exchanger on top of the motor which can also become clogged....it's a journey- but you don't want to over heat a motor. You might want to have a shop look at it as it sounds constrained somewhere in the system for sure..

aero3113

When’s the last time you replaced your thermostats? It could be sticking closed, now it’s working but could happen again. I had the opposite last season, both started to stick open and the engines were running cold. I found it funny that both decided to do that at the same time.

TonyG13

This has happened to me twice in the last few years. The most common reason in our area for overheating is getting a plastic bag, balloon, etc. sucked and stuck around the intake holes on the outdrive. Freaks you out when the alarm goes off and you see the temperature rise.

It happened to us during launch last year. We launch in the river which has lots of flotsam. Our mechanic told us an easy way to check if that is indeed the issue...

As soon as the alarm goes off, bring the boat full stop, then full reverse. If something was stuck/sucked to the intake, it should fall off. If safe to do so, turn off the engine and let it cool a bit. Then turn it back on and see if the temp goes back to normal.

If it does, you probably had an intake blockage. If not, start looking as described in everybody else's posts. 

davidbrooks

All good advice.  If this is a Mercruiser engine i believe that the thermostats are 165 degrees so even 180 is not right.  Changing the impeller is step one.  Get a diagram of the cooling system and water flow direction.  Pull each hose and run water through it with a garden hose.  You could have a piece of rubber from the impeller or dirt sucked up that is blocking a line.  After that look at where it comes in through the transom assembly.  As @rasbury and @LaRea said that line can get restricted.  It is or is supposed to be replaced every few years when you do the bellows and shift boot.  THE BOLTS SIEZE AND CAN SNAP EASILY.  So if you try and remove the 90 fitting don't put a lot into the bolts.  If you snap one you have to pull the engine to drill it out.  Ask me how i know.  Due to how much of a pain it is to replace these intake hoses a lot of people skip it.  On my boat when i finally got mine off it had an opening inside the diameter of a bic pen.  The new ones are a better design but still need to be replaced.  Thermostat is a cheap and easy replacement.  Definitely recommend going that route.  Problems tend to hide at the dock under 2000 rpms and come to life at half or 3/4 throttle with the family on board.

raybo3

If your fresh water cooled then take the end caps of the heat exchanger and clean out the ends and the tubes. Doesn't take much to cause the temp to rise. My money is that this will fix your problem. 

PickleRick

If he's closed loop aka fresh water that would explain why he's running 180 vs 165 although in fresh (non salt) water most people go to a 180 stat instead of 165 as we don't have the salt issue and the engines run more efficiency at 180 than 165.  

apdcop

Thank you all for your input.