Raw water pump swap in UNIVERSAL M-25 XPB

[rah138]

Hi.

I recently purchased a Catalina 38 and the cam that drove the water pump">raw water pump broke while the previous owner was motoring along. I want to swap out that water pump and replace it with a belt driven pump. Has any one done this before? Do I need to fabricate any parts to do that? Any guidance and/or pictures you can provide for this would be very much appreciated.

[bil56]

may be this cam can be repared, no ?

[JoeRobertJr]

Hi, Rah, and to the forum.

I recommend adding your boat info and location to your profile. That will help others tailor their responses.

If you don't get a response for a forum member that answers your question, you might try contacting a Westerbeke dealer near you. I think its a long shot, but can't hurt to ask them.
https://www.westerbeke.com/distributorlocator.htm

[skipperpete]

There are multiple possibilities with this, you can buy a pedestal base pump and engineer a bracket to mount it on or over the original hole in the timing cover and run a separate belt and pulley for it….. you could connect the pump directly to the end of the crankshaft, no belt at all as done on the VW pathfinder marine conversions …..or you could fix the damaged end of the existing drive. Raw water pumps don’t like to operated at high speed so you need to maintain that <>2:1 reduction ratio if you opt for a belt and pulleys
If you meant the cam inside the raw water pump, like with the Oberdorfer, you can buy a new cam and fastener.

[RaymondR]

You could go electric using a NC relay with the pump powered via the ignition switch and coil powered from the oil light circuit to prevent the electric pump from running until the engine starts.

[bil56]

Originally Posted by RaymondR

You could go electric using a NC relay with the pump powered via the ignition switch and coil powered from the oil light circuit to prevent the electric pump from running until the engine starts.

the problem is that an electric water pump has a constant flow, unlike the pump attached to the engine whose flow -thus cooling- varies with the engine speed

[RaymondR]

Originally Posted by bil56

the problem is that an electric water pump has a constant flow, unlike the pump attached to the engine whose flow -thus cooling- varies with the engine speed

Does not matter. the thermostat will regulate the flow through the engine to keep it at operating temperature.

[skipperpete]

If the engine WAS raw water cooled an electric pump would still be a risky proposition, the thermostat only diverts the full flow of the raw water pump to the exhaust manifold and mixer elbow and the flow would be excessive with a constant speed water pump and an idling engine to the point of potentially flooding the exhaust. If the engine is on a Genset running at a constant 1800 rpm… no problem.
I didn’t notice if the OP mentioned direct cooling or heat exchanger but either way, on an engine that can idle down to 800rpm it has a fair possibility of failure

[RaymondR]

Originally Posted by skipperpete

If the engine WAS raw water cooled an electric pump would still be a risky proposition, the thermostat only diverts the full flow of the raw water pump to the exhaust manifold and mixer elbow and the flow would be excessive with a constant speed water pump and an idling engine to the point of potentially flooding the exhaust. If the engine is on a Genset running at a constant 1800 rpm… no problem.
I didn’t notice if the OP mentioned direct cooling or heat exchanger but either way, on an engine that can idle down to 800rpm it has a fair possibility of failure

My last boat was keel cooled and had an electric pump to supply raw water to the exhaust system and it was never a problem. The pump I used had been previously used on my first boat as a standby raw water engine cooling pump and on the occasions it was put into service did not cause a problem.

From an engine flooding viewpoint the electric pump was probably safer as the pump will not start pumping until the oil light goes out. I had flooded an engine with a belt driven pump on a couple of occasions during extensive cranking whilst bleeding the fuel system.

[Pete7]

Originally Posted by skipperpete

I didn’t notice if the OP mentioned direct cooling or heat exchanger but either way, on an engine that can idle down to 800rpm it has a fair possibility of failure

Agreed, we need the OP to clarify what they mean by cam and what broke? some photos would be good.

Of course there are some engines that do have a raw water pump driven by the cam shaft, I have one. Real advantage is the belt which only turns the alternator, isn't actually needed to run the engine and get you back home safely. The engine? its a Volvo Penta 2003

Pete

[rah138]

Thanks everyone for the well thought out answers and sorry for posting this twice. I forgot I had posted this ��

I'll take some pictures next time I'm on the boat. It sounds like I might have to replace the cam shaft. The electric pump is tempting, but also sounds like it comes with some risk.

[rah138]

Oh just found some pictures on my phone but not sure how to post them...