Running above normal temp

[c03camson]

Boat runs maybe 10-20 degrees hotter than it should while Im running. When on the hose in the driveway it gets up to temp it stays there and doesn't overheat so maybe the thermostat is going bad? Or the engine is having to work too hard for some reason while underway?

I cleaned the bottom of the boat even though it didn't look dirty and that didn't do anything. I changed the impeller last fall and it is sucking up water like normal. If I wasn't trimming properly would that have anything to do with it?

WOT is 4600-5000rpm so what rpm should I be running at cruising speeds? Any help would be appreciated!

2003 Baja Outlaw. 5.0 Merc alpha1Gen2

 

[Bt Doctur]

Re: Running above normal temp

clogged risers come to mind

 

[Don S]

Re: Running above normal temp

I would sure check the impeller again, there are a lot of things that can take out impellers, and they are the first thing you should check with any overheat on a boat.

 

[c03camson]

Re: Running above normal temp

Now that I think about it I remember starting up the boat this past winter and the circ pump on the engine was not moving. I quickly shut it off and warmed up the engine bay and restarted it with no problems. I wonder if I screwed up that pump or impeller in there.

 

[Don S]

Re: Running above normal temp

Now that I think about it I remember starting up the boat this past winter and the circ pump on the engine was not moving. I quickly shut it off and warmed up the engine bay and restarted it with no problems. I wonder if I screwed up that pump or impeller in there.

I was referring to the impeller in the outdrive, not the circulation pump, but if the circ pump impeller isn't turning inside the pump, it will overheat.

 

[c03camson]

Re: Running above normal temp

I will check the impeller in the outdrive. When running on muffs there seems to be great water flow coming out the exhaust. As for the circulation pump, if the impeller wasn't spinning inside there would it only overheat by 10-20 degrees indicated? Also now that I think about it, everything I touch on that engine seems to be hot after running. The risers and elbows should not be hot correct? What about the temp of the water coming out of the exhaust?

 

[Taz59]

Re: Running above normal temp

The risers do get hot,just hot enough to touch.you still get water coming out of exhaust if the stat is stuck but not as much if it were open.Just had the same problem and replaced the stat and riser.

 

[Brentathon]

Re: Running above normal temp

I would never "check" an impeller in a drive.......just change it, they're cheap. If it's raw water cooled in saltwater, elbows (aka risers) get changed every 3 years, manifolds 5 or 6. T-stats are very cheap and very easy to change. My Alpha Gen I manifolds are usually quite warm, the elbows are a little less warm; manifolds get hot water from the engine (when t-stat opens), while elbows get a mix of manifold water and "excess" cold water from the drive impeller.
When my circ pump impeller sheared off, my temp gauge went to full COLD, yet my engine was over-heating........tricky failure.....without circ pump, it changes the whole dynamics of the water flow.
Running on muffs doesn't tell you much, since the hose pressure assists the impeller pump in the drive. True temp tests must be done in water.

 

[c03camson]

Re: Running above normal temp

Ok so sounds like I should open everything up and see if the circ pump impeller crapped itself. change the stat and the impeller. the new impeller only has about 5 hrs on it but that doesn't really matter. Thanks for all the input so far, im gonna go start messing with it now.

 

[Don S]

Re: Running above normal temp

I wouldn't pull the circulation pump clear off to check the impeller. Just remove the big hose, stick a screw driver in to hold the impeller and see if the pulley will turn the shaft inside the metal impeller.

 

[Brentathon]

Re: Running above normal temp

Good idea from Don to check circ pump, but if it's an original (2003) circ pump and run on salt water, I would change circ pump, too. They're standard maintenance items, I wouldn't wait till a circ pump fails before changing it.........kinda like drive impellers, manifolds, risers, etc.

 

[c03camson]

Re: Running above normal temp

the thermostat works. I stuck a screwdriver into where the big hose goes on the circ pump and i can spin the pulley with no problem. So that impeller in there is bad? If that circ pump wasn't doing its job does that mean I overheated my engine even though the temp gauge is only showing 175?

 

[Brentathon]

Re: Running above normal temp

Is there a chance that the screwdriver wasn't in the path of the impeller vanes? You may have to pull the circ pump, and might as well replace at that point, if original.
It's tough to say what the block temp went to, if the circ pump wasn't pumping. I know mine got fairly hot, because the engine "over-ran" when I shut the ignition, meaning the engine was hot enough to ignite the fuel/air charge without spark.

 

[c03camson]

Re: Running above normal temp

I couldn't really tell if the screwdriver was up in there where the impeller was. Like you said I might as well just take it out and change it. I looked up the part number on mercruiser website but cant find it when i type it in on the Iboats website. it also has two different kinds, one with air fittings and one without. So im not sure about that either. thanks for the help

 

[c03camson]

Re: Running above normal temp

Im confused here, is there two different types of pumps? This one (862914T10) looks a lot different than this one (18-3583). When I look it up on the mercruiser website it gives me the first part number which is a completely different pump than the one I see on my boat which looks like the second part number.

 

[Bondo]

Re: Running above normal temp

When I look it up on the mercruiser website it gives me the first part number which is a completely different pump than the one I see on my boat

Ayuh,... Donno how ya got there,...
That's a Raw waterpump for a Bravo....

Yer 2nd choice is the circulating waterpump...

 

[c03camson]

Re: Running above normal temp

Ok I took the circulating pump off and that is intact so it is not my problem. I guess the next step would be to check that thermostat to see if it is opening up at 160. The next step would be to check that impeller in my lower unit and if that isn't it, the risers could be getting clogged? Any other opinions? Thanks for all the help so far.

 

[c03camson]

Re: Running above normal temp

If that impeller was installed with the fins going in the opposite direction would it still work? and for how long?

 

[Bondo]

Re: Running above normal temp

If that impeller was installed with the fins going in the opposite direction would it still work? and for how long?

Nope...

 

[c03camson]

Re: Running above normal temp

Ok so if Im still running 10-15 degrees above 160 and its not the thermostat, not the circ pump, could there still be something wrong with the impeller? I just put in on last fall. Ive got good waterflow and at idle it will run 160. the faster i got the warmer it gets. I want to exhaust all my options before i look at the risers/manifolds.