Yanmar raw water cooling problem

[noreault]

Not a lot of scoring. Some faint circular on the inside. Very little on the outer part. While definitely not a highly polished surface, but to my eye looked smooth enough for the gasket to work well.

Is it possible for pump to lose a prime from a leak later in the cooling system. I ask since when I changed the engine zinc the bolt that the zinc screws into was completely frozen. It is mounted into a small cover held on with 4 bolts. All of which moved easily. I was somewhat surprised that there was no gasket on that piece. It doesn't seem to leak, but could let air in I suppose.

[Northeaster]

My cover was scored (circular, from the impeller wearing it) enough that you could see it easily, and catch it with a fingernail - maybe 1/32" - 1/16" or so.

Yours sound OK. I am not a mechanic, so maybe someome else can chime in. I think that if your raw water pump and impeller are in good shape, you shoudl not have water or air bypass it. I don't think any air leaks are good. However, air is always in the exhaust elbow, yet doesn't make it's way back through the heat exchanger, and then water pump. Your possible leak is quite far down the line, so it may not be an issue. I do think any leaks / loose clamps near the pump would facilitate the loss of prime.

Let us know how you make out.

[rikhall]

Just my personal opinion.

I don't like a strainer on the outside of the boat covering the raw water intake. I prefer a Groco raw water strainer inside. With no covering strainer I can (worst case scenario) remove the hose and shove a close hanger wire down to clear it. We have the raw water strainer inside and we can see if there is sea weed or whatever in it.

Just my personal preference.

[noreault]

Well thanks to all. Everything seems to be in good shape (knocking on wood as I say that). At least no lost of prime since the repair. My plan is to get a raw water strainer on the inside.

[blueoctober]

Excellent posts-very, very helpful

[SteveInMD]

I completely agree. Exterior strainers cause many more problems than they solve.

Originally Posted by rikhall

Just my personal opinion.

I don't like a strainer on the outside of the boat covering the raw water intake. I prefer a Groco raw water strainer inside. With no covering strainer I can (worst case scenario) remove the hose and shove a close hanger wire down to clear it. We have the raw water strainer inside and we can see if there is sea weed or whatever in it.

Just my personal preference.

[roline]

Speed seal does offer an alternative if your willing to pay the price. I like the idea of the Oring seal instead of sealants and gaskets. Paper gasket thickness should be around 0.003" thick possible glycerin treated paper for this application. We used it for rebuilding oil pumps to prevent excessive end play gaps to produce pressure loss.