Another overheat...

[bruceyp]

Yesterday I motored out to some bigger water and had a great sail on a beautiful day. Wind 12-15. Seas 1-2 feet. Really great. Sailed back to the beginning of the channel to head in and the engine overheated again. I have a Yanmar 2QM15 installed by a PO years ago in my C&C 29.
The last time this happened while investigating what could be wrong I opened the raw water strainer, saw that nothing was blocking the water flow and closed it back up, restarted the engine and the water flowed normally. So I figured if it worked last time , it could work again. Yup, it worked.
What is going on here? Is there an air lock that needs to be broken ? Is this going to be part of my SOP? I'm sure that running the impeller dry isn't a good thing.
Has anyone run into this before and/ or have suggestions as to what to look for?
Thanks,
BP

[Maine Sail]

Originally Posted by bruceyp

Yesterday I motored out to some bigger water and had a great sail on a beautiful day. Wind 12-15. Seas 1-2 feet. Really great. Sailed back to the beginning of the channel to head in and the engine overheated again. I have a Yanmar 2QM15 installed by a PO years ago in my C&C 29.
The last time this happened while investigating what could be wrong I opened the raw water strainer, saw that nothing was blocking the water flow and closed it back up, restarted the engine and the water flowed normally. So I figured if it worked last time , it could work again. Yup, it worked.
What is going on here? Is there an air lock that needs to be broken ? Is this going to be part of my SOP? I'm sure that running the impeller dry isn't a good thing.
Has anyone run into this before and/ or have suggestions as to what to look for?
Thanks,
BP

Probably draining back from heeling and your impeller is worn and can't re-create the flow very well.

Try closing the seacock when you go under sail, but stick the key on the valve so you HAVE TO open it to start the engine. If it starts with no problems it's due to drain back. If it's a major PITA when you haul move the seacock to the centerline...

It could also be that your strainer is well above the static water line and gravity automatically takes over even without heeling. If that is the case move it lower in the boat..

[SEMIJim]

Originally Posted by bruceyp

Sailed back to the beginning of the channel to head in and the engine overheated again.
...
The last time this happened while investigating what could be wrong I opened the raw water strainer, saw that nothing was blocking the water flow and closed it back up, restarted the engine and the water flowed normally. So I figured if it worked last time , it could work again. Yup, it worked.
What is going on here?

My guess is you're picking something up in the raw water intake and when you shut the engine off to check the raw water strainer it falls out/off--perhaps aided by some water running back down toward the thru-hull when you open the strainer?

Jim

[donradclife]

Something similar happened on a boat I raced to Hawaii, and the temporary fix was to close the thru-hull just before shutdown and open it just after startup, as recommended above. Never did hear what the ultimate solution was.

[Rockter]

My own pump will not self-prime if I take the boat out of the water.
It would when new but does not manage now.

It could be caused by heeling in your case.

[timebandit]

If it did not do this last season then something is WRONG.

If you have not changed the pump impeller then do it NOW.

Your boat is trying to tell you something.

You better listen.

Rick

[bruceyp]

Rick,
I install a new impeller every spring. Now that I ran this one dry I think I will replace it again,though. I think Halekai may have something. I'm going to try to shut the seacock off once I set sail and see if that does something. The strainer is above the water line too but I thought that was by design. And besides it hasn't moved since last year and I don't remember having this problem then.
BP

[Don0190]

I sailed this year with someone who has a C&C 36 and he had overheats this year also. He spend $700 for a mechanic to check it and it still overheated. Couldn't find anything wrong, but was losing freshwater from the system. Decided to add a fresh water expansion tank to the system (seems a good idea) and still overheated. Finally in the end what it was is that the hoses were too long. When the cover was off everything worked just fine. But, when the cover was put back on the hoses kinked and this pinched off the flow. Sometimes it is just too simple.

[timebandit]

You might check the seal on the strainer because if it is above the water level it might be leaking air and and that would account for the pump not priming.

I think if it happened last year you would remember.

Rule 1

The last thing you mucked with is the first thing to mess up.

Rick

Originally Posted by bruceyp

Rick,
I install a new impeller every spring. Now that I ran this one dry I think I will replace it again,though. I think Halekai may have something. I'm going to try to shut the seacock off once I set sail and see if that does something. The strainer is above the water line too but I thought that was by design. And besides it hasn't moved since last year and I don't remember having this problem then.
BP

[bruceyp]

Time Bandit,
That's an idea. I don't even remember seeing a seal or gasket or anything. I'll have to check that out.
Thanks,
BP