I am hoping some of you can help me out here. Not being mechanically minded, especially about engines, I was having some trouble last year with the engine overheating. The marina (Bayport in Midland) determined that my raw water pump was the culprit. This spring they found that the impeller was damaged and replaced it.
I was out for my first sail of the year this past week (don’t ask) and noticed that there was a slow drip while the engine was running and shortly thereafter at the forward end of the pump. I inquired at the marina and they looked at it and told me that the bushing was probably damaged and the pump would need to be re-built or replaced.
I am reasonably certain that the pump is a Sherwood H-70. My Nonsuch is a 26C. Getting at the raw water pump is tricky.
A couple of questions at this point:
When the impeller is replaced does this require removing the shaft? If so is it possible that the bushing was damaged when the shaft was replaced?
I have done a fair amount of research in the last few days and combed these forums for information on this problem. I understand that the bushing is carbon and can be easily damaged.
The downside is that with Covid I have not been able to be on site when these repairs are being done so I can’t ask relevant questions of the technicians. This is one of the main reasons why the repairs to my boat have taken so long this year.
My research has taken me all over the internet on a mind numbing trip. I have been able to determine that the H-70 is no longer being made and that parts are becoming scarce. The current replacement for the H-70 is the 48080. This pump has a different configuration than the H-70.
My final questions are:
Do I get a new pump (48080) and re-jig the hoses and try to re-build the H-70 sometime over the winter? How difficult is it to re-build the H-70?
Jim Lorriman
Capers NS26C #69
Bayport, Midland
Ontario
Hi Jim, I recall many years back when I changed the impeller on our w27a, I did pull out the shaft. It started to leak as you described after I reinserted the shaft with the new impeller attached. I sailed this way for many years and simply redirected the small drip to the bilge and away from the wooden engine bed rail. It was no problem and it never leaked more than just a drip. When I switched to a dripless shaft seal I bit the bullet and bought a new pump (expensive!!) to keep the bilge dry. The plumbing was different but not impossible.
Hope this helps…Ron
Ron & Diane Schryver
“Alpha Waves” NS30U #393
Georgian Bay Midland ON
That was encouraging! You are right about the cost of a new pump and having the marina install it won’t be cheap either.
If the bushing is compromised is there a chance that water could get to the drive end of the shaft? There appears to be 2 seals with a slinger ring between them between the bushing and the end of the shaft. If water can get through, I definitely need to replace the pump. If not I can probably sail for the rest of the summer as long as I can monitor the leak.
Any thoughts?
Jim Lorriman
Capers NS26C #69
Bayport, Midland
Ontario
I had my H-70 rebuilt a number of years ago, and as a result it was slinging more water than it had been before the rebuild! I too remember being told that the carbon bushing was very difficult to replace successfully.
After a season with the rebuild, the amount of water being slung onto the engine block became unacceptable, so I replaced the pump with a #48080, exactly as your research has suggested to you. I’ve been very happy with this pump. I remember having to fit it with 2 right angle outlet fittings, each aimed in a different direction in order to match up to the hoses properly, and to avoid different obstacles on the engine. As a bonus, the impeller on the 48080 is much easier to replace than on the H-70.
I second Ed’s swap to the 48080…former owner of my boat screwed around to save money and never solved the problem. My yard just installed the 48080 and rebuilt the heat exchanger which looked to have collected every broken vaane for the last 35 years…amazing I didn’t have a catastrophe.
While a very worn shaft can cause a leak, it’s more likely that the outer seal is worn. If you disturb something that is old, there will be consequences. It is not hard to rebuild those pumps if you have the mechanical ability and some tools. If you are not comfortable doing it, bite the bullet and replace the pump and all associated hoses with it.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Hi Jim, in our case the seal closest to the impeller was damaged while the other seal appeared to be fine. You’ll have to inspect the source of the water to be sure.
Ron
Ron & Diane Schryver
“Alpha Waves” 1987 NS30U #393
Georgian Bay Midland ON
We are in a bit of a time crunch. My wife and I are hoping to get away for a cruise up Georgian Bay next Tuesday. I talked to Bayport this morning and they will have a 48080 there tomorrow morning with the attendant elbows. The hard part is that their techs do not have time to get the change made before we are scheduled to leave. I had to lay on the charm and do some begging and I hope they will squeeze me in somewhere. I will look at getting the H-70 rebuilt this winter.
On Wednesday I will be looking into the next issue on the engine, that being the throttle. When put to full speed it tends to voluntarily drop back to about 2000 rpm and to encourage it to stay at higher rpms I have to use a bungee cord. Meanwhile at the other end of the spectrum when I drop the speed back to idle I sometimes move the throttle a bit too far and the engine shuts off. This probably needs more research here and should be a new conversation.
Thanks to all of you for the help and advice on the raw water pump.
Jim Lorriman
Capers NS26C #69
Bayport, Midland
Ontario