Question on overheating repair or replace

[Viper]

For what it's worth, while it's good practice to install an impeller curled in the right direction based on pump rotation, an impeller installed in the opposite direction will correct itself once it clears the end of the cam and rides up on the other side. This should happen in less than one full rotation with negligible ill effects. An impeller lubricant helps here though its main purpose is to lubricate the impeller while it runs dry at initial startup.

[tonyiiiafl]

I have a port (1130 hours) running at 160 and starboard (42 hours) running at 168. Have always had "steam" from both exhausts, new heat exchangers.

[390Express]

I don't know what people use for impeller lube, but if you're looking for something environmentally friendly, cheap, easy and quick, dawn dish soap works great. Soak the hell out of it, and it slides right in.

I always considered a small amount of steam in the exh normal. A 6 degree temp difference wouldn't bother me at all.

[Helmsman]

Ok guys, i am de-winterizing. I am in the water. I replaced the impeller and the old one looks brand new. With the old one out, I back flushed from the heat exchanger hose back through the transmission cooler, and out the hose connected to the impeller housing into a pail. There was zero debris in the hose. Water flow was good.

Here are my next steps.

1) I will disconnect the other raw water hoses from what looks like a fuel cell, and also from the other side of the heat exchanger to see if any debris falls out.

2) The heat exchanger is up tight against the exhaust hoses on both sides. Would it make sense to use Rid-Lyme on it now before I start pulling the heat exchanger apart? I will use the sea flush system that I use for winterizing and that will tell me whether I am still having the same problem with the water flow. Looks like some work to get the heat exchanger removed and since Cooler mentioned that pulling those hoses is a tough job, it may not be doable to get the ends of the heat exchanger off without pulling the HE or removing the exhaust hoses.

As a reminder the flow was restricted when I used the Sea Flush system to winterize. Took a very long time to get 5 gallons through it. Spitballing here, could it be something to do with air being in the system? Seems like it began happening at the start of last season.

[Helmsman]

Qr Bbpost I wouldn't worry much about the exh. manifolds if she's a fresh water vessel unless further diagnosis takes you in that direction. You could have garbage or impeller pieces from a previous failure in the HE or cooler though. Impeller pieces have to be removed manually or flushed out but try Rydlyme to descale and clean the HE and cooler before removing and sending out. Of course check all the other normal things like intake hoses, connections for leaks, strainers, seacock, etc.

I noticed the slow flow last fall when I was winterizing with a sea flush unit. So the seacock and strainer are ok I think.

[tomschauer]

Its an open system, so air is not an issue. I do know however, when I first splash my boat I need to goose the throttle a little bit to pull a vacuum and bring the water up to the pump. After the initial start, its never an issue again.
If you are in the water, did you start the engine and check for flow? Fire them up, both should have nearly equal flow out of the exhaust. If not, you have something in the system. I would doubt its scale. You usually only need to use a scale remover if you have good flow and still cant transfer the heat. Scale removers can soften the copper of your heat exchangers, only use them if needed. So, unless you are in an area with zebra mussels, it most likley impller pieces somewhere in the system.

[bud37]

Qr Bbpost
2) The heat exchanger is up tight against the exhaust hoses on both sides. Would it make sense to use Rid-Lyme on it now before I start pulling the heat exchanger apart? I will use the sea flush system that I use for winterizing and that will tell me whether I am still having the same problem with the water flow. Looks like some work to get the heat exchanger removed and since Cooler mentioned that pulling those hoses is a tough job, it may not be doable to get the ends of the heat exchanger off without pulling the HE or removing the exhaust hoses.

I think I would still remove the hoses and have a look before treating.....if by air, you mean the system is pulling in air.....yes that is possible and will screw with your flows......check all your hose connections, especially the ones you remove often on the suction side, could be a small crack at the pump inlet, been there done that, they don't necessarily leak when off making it hard to find.

I cant remember but you have checked the thermostat ?

[mjk1040]

I noticed you had an issue getting hoses off. A heat gun is a must when trying to remove hoses IMO. Viper mentioned earlier to descale the engine with RydLyme! And as mentioned thermostats.

[Helmsman]

Qr Bbpost

Qr Bbpost
2) The heat exchanger is up tight against the exhaust hoses on both sides. Would it make sense to use Rid-Lyme on it now before I start pulling the heat exchanger apart? I will use the sea flush system that I use for winterizing and that will tell me whether I am still having the same problem with the water flow. Looks like some work to get the heat exchanger removed and since Cooler mentioned that pulling those hoses is a tough job, it may not be doable to get the ends of the heat exchanger off without pulling the HE or removing the exhaust hoses.

I think I would still remove the hoses and have a look before treating.....if by air, you mean the system is pulling in air.....yes that is possible and will screw with your flows......check all your hose connections, especially the ones you remove often on the suction side, could be a small crack at the pump inlet, been there done that, they don't necessarily leak when off making it hard to find.

I cant remember but you have checked the thermostat ?

Bud, I haven’t checked the thermostat. I know I have low flow. When I winterized the system with the Sea Flush kit, it took much longer to pull 5 gallons of AF out of the bucket. Also, when I started it yesterday, the flow out of the exhaust was lower than the other engine.

[Helmsman]

Qr Bbpost I noticed you had an issue getting hoses off. A heat gun is a must when trying to remove hoses IMO. Viper mentioned earlier to descale the engine with RydLyme! And as mentioned thermostats.

Thanks. Great suggestion!