Overheating issue when propeller runs after 2 minutes

[aveger]

I have a 1997 Four Winns 21 foot Ski Boat that has a 5.7 Volvo Penta motor in it.
It is a 5.7 GXi ? The sticker on the outside of the out drive also says Volvo Penta SX.



It starts up perfectly fine and sounds great , in the beginning..!
When I put it in the water and ride slowly around (in no wake zones) it runs about 130 to 140 degrees and eventually gets up to 240 degrees after a few minutes of running.
When I enter the ?End no wake? zone, and throttle down about ? of the way, in about 2 minutes the temperature climbs up to about 240 degrees.
I then turn the engine off to let it cool down ? When I try to start it again (after 4 or 5 minutes of it being off) it is real difficult to start.

When I hook it up to the ?ears? and let it run idle in my driveway, I have no heat issue at all (ran it for 15 minutes)

I have Replaced the impeller that is on the motor ? Still didn?t fix the heat issue.
I have replaced the thermostat ? Still didn?t fix the heat issue
I even ran it without the thermostat ? Still didn?t fix the heat issue

I have been told by some people that this motor only has one impeller and other people have told me that it ALSO has an impeller on the lower unit too.

Besides the obvious question of do I have an impeller on just the motor or do I have one on the motor AND the lower unit , anyone have any ideas what could be causing the heat issue?

 

[bruceb58]

The raw water pump with the rubber impeller is driven by the engine. Nothing is in the drive.

Are you in salt or fresh water?

What is your model number? Didn't know 1997 engines had serpentine belts.

 

[aveger]

I found a plate on the outside of the outdrive it says
Product Number: 3869340
Ratio: 1.43

 

[bruceb58]

Look on your engine near the thermostat housing

 

[aveger]

Saltwater...

 

[bruceb58]

Because you are in saltwater, it is very possible your manifolds/risers are plugged causing your water flow to be insufficient. That is just one possible cause you may need to check. Pull the risers and have a look and post pictures. Make sure you put the risers back together with new Volvo gaskets.

EDIT: Of course that theory gets blown away because you can run it on muffs unless it is close to marginal but when run with a load it heats up

 

[dypcdiver]

Agree with bruce58, I'd also check you have the correct impeller fitted, but there is also a possibility that you have an air leak prior to the pump and it may not be sucking sufficient water to cool the motor, the muffs would overcome that.

Places to check outboard are the hose that connects the drive to the top of the transom shield, check for splits and the hose clamps. Inboard the same supply that goes from the top of the transom shield to the power steering heat exchanger then directly to the UPPER connection on the raw water pump. As this is not a 1997 motor (its newer) you may also have an engine flushing connection which must be sealed with the correct plug. There is also a shaped "O" ring in the drive mating face that could also leak but unless the drive has been off it is unlikely. Let us know how you get on.

 

[aveger]

Thank You everyone!!! I appreciate all the help and information.. I will be getting this work done this weekend and or next.. I will post updates..
Until then, here is a picture of the impeller that I cleaned up and put back in. I also rubbed a thin layer of Vaseline around the housing to make sure the impeller spins