Burned up new raw water impeller

[Olddan1943]

Originally Posted by Sailmonkey

This should be one of the two things you check every time you start your engine.

Oil pressure, and water from exhaust.

Checking water from the exhaust is difficult since most boat builder are now using the "quiet exhaust" option, discharging below the water line.

[Olddan1943]

Originally Posted by rocnrichy

Bought a 1970 Morgan 41 yawl and decided to change the raw water impeller on the 2007 Yanmar 3JH4E. I shut off the seawater cock and installed the impeller and after doing so we took it for a run. About 30 minutes from port the overheat alarm sounded and found the raw water pump housing got so hot it burned the paint off. Got towed in and found that the pump blades relocated to the heat exchanger. I think maybe the pump maybe somehow got an air bubble in it and ran dry. Is there a way to bleed the air out of the system? Can anyone tell me what the proper procedure is before I burn up another pump. Thanks

Not too long ago, I had trouble with my A/C SW pump. I back flushed from the sea strainer.... it would run for a few minutes then error out with HP.

I had a diver come out, nothing unusual. I finally called out an A/C tech. He checked the sea water strainer and the rest of the system, noted a correct flow and then, shut down again. I suggested, in desperation, he remove the hose from the hull valve to the sea water strainer. He found a plastic bag had been sucked though the hull grate. Pull the chewed up plastic bag out, put the hose back on and presto! Everything returned to normal. Both of us learned a lesson.

Quick question. When was the last time you had the hull cleaned?

[Olddan1943]

Originally Posted by Olddan1943

Checking water from the exhaust is difficult since most boat builder are now using the "quiet exhaust" option, discharging below the water line.

A lot of problems would be eliminated if there was an easy way to install a water flow meter and temp meter for the ME and Gen.

[John_Trusty]

This is great advice, and I can add only a little more -- a little lubricant for the first few turns of the impeller, like @Ziggy mentioned. Different impeller manufacturers recommend different things, but be careful with any petroleum-based products that can eat the PU rubber. That's why most recommend glycerin-based lubricants. The cheapest and most easily obtained is 'personal lubricant', like KY Jelly. You know it's safe on all rubber and PU products. A large dose all over the impeller also fills the gaps and helps prime the pump, and it's water soluble so it's gone after a minute of running. Now explaining to your significant other why you keep a tube in the tool box is your problem.

[MV Wanderlust]

Originally Posted by a64pilot

Pump really should prime itself unless there is an air leak.

This is what bit us, once. We had a local mechanic change a raw water hose from the strainer to the pump. He admitted he wrestled with the end on the pump for quite a while. What we didn't know was he wrestled with it until the inner layer of rubber on the hose folded over and left a tiny air gap around the flange. The pump sucked air and, before we knew what was going on, we had burned up a $750 pump. Our exhaust outlets were underwater so there was no way to tell that engine wasn't spitting out water. Anyway, that's ancient history now.

[kmacdonald]

Sounds like the inlet and outlet hoses were crossed or hooked up backwards. Sucked air from the exhaust outlet.

[a64pilot]

Originally Posted by Olddan1943

A lot of problems would be eliminated if there was an easy way to install a water flow meter and temp meter for the ME and Gen.

There is, I have seen one, but don’t remember the specifics, it apparently triggers an alarm at no water flow, I don’t think it’s temp, I think it’s flow.
A quick google found this, and several others
http://www.lfsmarineoutdoor.com/aqua...YmkTZMjmF5ApZcDx6qyYs3hCXUTXafp4b6xr9VO0SxoC_WoQAvD_BwE

Google Marine engine raw water alarm or similar

[Olddan1943]

Originally Posted by a64pilot

There is, I have seen one, but don’t remember the specifics, it apparently triggers an alarm at no water flow, I don’t think it’s temp, I think it’s flow.

That's a start. Let us know if you find it again.
Thanks

[Red Sky]

Originally Posted by danielamartindm

Bottom Line: Check your exhaust IMMEDIATELY after any raw water modifications/servicing. It's the final word.

What he said +1

[Ken Z]

Was the impeller vanes turned in the correct direction to how the pump turns? sucked up debris, clogged intake seacock, lack of lubrication on impellor during installation?

[KadeyKrogen38]

Jabsco raw water pumps changed from bronze cam plate to nylon plastic. I had the forks break off the plastic can plate immediately after changing impeller. Completely shredded the new impeller on first outing. Had to remove heat exchanger to get out all the rubber bits.

When changing impellers. Please remember to check condition of cam plate

[Squanderbucks]

Rubber impeller pumps like Johnson, Jabsco, Sherwood should self prime to most any normal engine pump setup. Unless you forget to turn on the strainer valve and all you did is change the impeller it should pump water. In just replacing the impeller no need to remove hoses so reversing can be eliminated.
Likely the gasket was not fully sealed or worn faceplate. These impellers will run for a few minutes without water without too much problem. If you can’t see water out the exhaust. Put your hand on the pump face and it should be cool. If not there is a problem.
A flow detector is made by Aqualarm ompany and while I don’t have that particular product I do use several other they make. Exhaust high temp alarm and bilge pump counter. I really love the pump counter. It really lets you know how water tight your boat is at a glance.

[foufou]

I was concerned about the raw water pump priming itself after re launching. But after thinking about it I concluded what Jkishel mentioned; the anti siphon or vacuum breaker at the mixing elbow would allow air to escape and water to fill the pump. This of course only if the pump is below the water line. But it could be not all boats have the anti siphon devices. In any case, always check for exhaust water flow.

[DotDun]

Originally Posted by foufou

I was concerned about the raw water pump priming itself after re launching. But after thinking about it I concluded what Jkishel mentioned; the anti siphon or vacuum breaker at the mixing elbow would allow air to escape and water to fill the pump. This of course only if the pump is below the water line. But it could be not all boats have the anti siphon devices. In any case, always check for exhaust water flow.

It's more important if the strainer is above or below the waterline. Water nor air usually flow freely thru an impeller pump.

[Zoidislander]

I found out the hard way that the Globe run dry impellers really DO work. I accidentally shut off my raw water seacock, and ran for twenty minutes till the temp alarm sounded. No damage to the pump, or impeller.