Raw water pump replacement

Intro

During an engine inspection, we found that our raw water pump was leaking where it mounts to the engine. It was pretty corroded, so I decided to just replace it.

Since I was about to replace my heat exchanger anyway, I chose to do them at the same time, since I would already have the hoses off and the coolant partially drained.

Parts

Our engine is the Universal M25XP with the Oberdorfer N202M-15.

There are some online sources with very good prices. Unfortunately, when I tried to buy one, the manufacturer was in the process of moving to a different state, and there were none available anywhere online. Luckily, one of our local marine parts stores had one in stock. I paid a bit more, but at least was able to get one.

When you buy the pump, it does not come with the gasket that goes between it and the engine. Since that is a Universal part (#298485), you can only buy it from a Universal dealer that is authorized to sell in your state. Luckily, ours is just down the street from the place where I bought the pump, so I pick one up for a couple of bucks on the same trip.

There are two 90 degree fittings that convert from 3/8″ NPT to 5/8″ hose barbs. I’ve heard those must be bronze, not brass, since this is a saltwater environment. I was not able to find bronze ones, so I planned to reuse the ones from the old pump.

Removal

Removing the hoses was pretty easy. I just removed the four nuts to get the old pump off. Once it was off, I scraped off all the old gasket material, and cleaned up the engine mounting surface.

Install

Next I removed the hose barbs from the old pump, and installed them in the new pump with Teflon tape. Then I reconnected the hoses, positioned the new gasket, and aligned the shaft with the slot. At that point, it was just a matter of putting the nuts and lock-washers back on. I tightened each one a bit, then moved on the next one. I did this until all four were evenly tight.

Checks

After starting the engine, I checked for good water flow out the exhaust. The results were quite impressive. Between replacing this pump and replacing the heat exchanger, there was a lot more water flow.

I then went below to check for any leaks, and was very happy to find there were none. Hopefully we will be good for several years now for the raw water cooling.

Updates

May 2023

While doing the annual engine maintenance, I noticed water dripping from the weep hole. It seems that the inner seals have already failed. I am very disappointed that they only lasted 3 years. The rebuild kit and work to do the rebuild does not seem like a good value, so I am ordering a new one. I may rebuild it later if the body is still in good shape. Then I will have a spare.

While looking for replacement elbow connectors, I was unable to find bronze ones with a 3/8″ NPT. After talking to the great team at Pumps and Parts Online, I decided to switch to the N202M-16, which is the exact same pump but with 1/2″ outlets.

I then ordered Groco ‎PTHC-5062 fittings. They are made to work for either 1/2″ or 5/8″ ID hose, but they are too long to install next to each other. Luckily, we only need the 5/8 barb, so I was able to cut off the 1/2″ barb section, and they fit just fine. This time I used pipe-thread sealant instead of Teflon tape.

Once I removed the old pump, I saw that the fittings for it had much larger interior openings, and this made me question the new bronze fittings. I decided to switch to brass ones that would allow better water flow. I bought them on Amazon, but Catalina Direct sells the same ones, so I figured I should be safe to use them. I will just keep a close eye on them during future maintenance.