Circulating pump v. Raw water pump

[ers906]

Looking at the exploded view of the PCM engine, I can see a raw water pump and a circulating water pump. Since I am fairly new into the world of boat engines, I know that you need to replace the impeller in the raw water pump, but is there any maintenance needed for the circulating water pump? I assume that its job is to circulate water throughout the engine cooling system, while the raw water pump is to intake water from the lake into the system. am I correct?

[krt]

you are correct, it's like the water pump on your car. Had to only replace the circulation water pump on my other boat once.

[ers906]

How did you know when you needed to replace the circulation pump?

[core-rider]

You will not need to replace the circulation pump unless there is a mechanical failure, leaking from seals, etc. There is no normal maintenance for it. Like KRT said, it's just like the water pump on your car/truck. Don't worry about it.

[DanielC]

The biggest reason circulating water pumps are replaced on cars, and trucks, is because the seals on them are leaking. Cars and trucks pressurize the cooling system. Boats do not pressurize the cooling system, the hot water just flows out the exhaust.

[scuff97]

Altough there is no radiator cap, the raw water pump can still build as much a 25 psi in the system. This can sometimes cause the circ pump seal to leak.

[KONAKING]

The biggest reason circulating water pumps are replaced on cars, and trucks, is because the seals on them are leaking. Cars and trucks pressurize the cooling system. Boats do not pressurize the cooling system, the hot water just flows out the exhaust.

Unless you have a closed loop system !!!!

[ers906]

No closed loop system here. Just trying to figure out why I have intermittent overheating issues while at idle (up to 230), and the dissipate while under throttle. No air coming in the FlushPro, tightened all of the clamps, no leaking around the raw water pump gasket, and impeller is fine. Any other ideas?

[WakeSlayer]

Did you get EVERY hoseclamp? Any chance your gauge or sender is just flaky? Did you get a laser temp gun? Have you ever blown an impeller apart and have pieces in the engine?

[scuff97]

O ring ok at the strainer?

[ers906]

I think I got every hose clamp that I could find with a ratchet and not a screwdriver. I did get a laser thermometer and It read normal (130-160 depending on placement) while I had the boat hooked up to the Flush Pro. The strange part is that when I placed the Fake-a-lake on, there was no water uptake into the engine. I was able to disconnect the intake hose and pour water down it, and there was no impediment to the drainage. I am at a loss. Ideas?

[DanielC]

There have been issues before with using flush-pro adapters.

Personally, if it was my boat, I would remove it, and go back to a stock system.

Here is a thread for a flushing adapter I made, that I temporarily put on my boat.
http://www.planetnautique.com/vb3/sh...ushing+adapter

My adapter enables me to pressurize all the hoses and fittings between where it is hooked up, to the raw water pump. This usually makes any leaks on the suction side of the raw water pump obvious.

The flushing adapter is removed before I run my boat on water.

On Super Airs, there is a lot of plumbing in between the raw water pump, and the water pick up in the bottom of the boat. You have the fitting on the hull, the raw water strainer, the transmission oil cooler, the water goes through the V-drive cooling passages, all the hoses to connect all that stuff, various fittings on all the equipment. Check carefully the fittings on the raw water strainer, between it, and the hoses. All this stuff can leak air. With all this stuff in the plumbing, the raw water pump has to work pretty hard to suck water from the lake you are floating in. Oh, yea, your boat has a flush-pro. One more device to mess with water flow, and have fittings to leak, never mind possible leaks in the flush-pro itself.

Did I mention that in my opinion, you should remove the flush-pro?

[WakeSlayer]

Take your laser out on the lake with you. Fake a lakes are not a good representation of actual use. I still think you are missing a loose clamp. And definitely lose the flush kit. Run it off the hose directly, just past the strainer. And verify the integrity of your strainer O-ring as mentioned before.

[ers906]

I am definitely going to be removing the flush pro, but I have ended up dropping the boat off at the mechanic so it will hopefully be done by the weekend so I can use it. At some point I would rather pay so I dont have to miss more than 2 days on the lake. It is always a bruise to the ego, but the amount of relaxation obtained being able to use the boat rather than have it sitting in the garage is worth it. (I think)

[PHB]

Have you ever replaced the strainer? They seem to suck air after awhile especially at the inlets where the Teflon tape wears out on the barbs.