Impeller lubricant?

8122pbrainard wrote: TRBenj wrote: and no, I would not expect an air leak to show up as a water leak with the engine off. I agree since without the engine running, the delta P is equal inside to outside. With it running, the delta P is less inside than out.

Really? i figured there would be a little bit of pressure inside that hose due to water just wanting the fill the cavity of the boat if the hose wasn't connected to the strainer.

Just replaced mine and it was bad with 45 hours.. Sorry no pics

TRBenj wrote: and no, I would not expect an air leak to show up as a water leak with the engine off.

I agree since without the engine running, the delta P is equal inside to outside. With it running, the delta P is less inside than out.

An overheat at idle is still all but guaranteed to be an air leak. There are more opportunities in a dual impeller Chrysler than most. Hose condition can be a contributor as well, and no, I would not expect an air leak to show up as a water leak with the engine off.

8122pbrainard wrote: turningpoint84 wrote:    The pump i took apart several times to try to diagnose the issues, but couldn't figure it out, the pump is in great condition. Also the hoses are fine...i figure if i'm sucking air just about the only spot i could is where it attaches to the RWP. How did you "diagnose the issue" with the RWP? How do you know the pump is in "great condition"? Have you tightened up hose connections?

I took off the outlet hose connections and ran the engine, water came out at a decent rate, (only for a minute or 2).

Hose connections I can't make any tighter unless i break the hose clamp


and yes I have 2 strainers. John B and I didn't spend too much time on it, next summer, i'll spend sometime on it and figure it out, new hoses wouldn't hurt.

Strainer cup cracked or missing oring?

8122pbrainard wrote: turningpoint84 wrote: How are you checking to see if your's is primed, seems like a PITA everytime you want to go out on the boat... I have noticed mine struggles when i'm idling, i have to speed up to get the damn thing to work, my engine temp just starts to sky rocket, so i pick up the speed to cool her down. It's an issue I haven't had a chance to spend time on, but would love to get it fixed. Checking each time you go out isn't needed. It's after draining when it should be checked. Hoses should feel cool, feel pressurized and water should be exiting the exhaust. Speed up to cool!! That's not a solution. You have a problem that needs to be attended to. Check for leaks on the suction side of the RWP. If none, then rebuild the pump. The shaft seal may be sucking air. How does the impeller look? Hopefully you NEVER run the boat without being in the water or hooked up to the hose.

The pump i took apart several times to try to diagnose the issues, but couldn't figure it out, the pump is in great condition. Also the hoses are fine...i figure if i'm sucking air just about the only spot i could is where it attaches to the RWP....anything below that and wouldnt i be taking on water into the boat when it's at rest?

I'm thinking about installing my left over 318 RWP i have laying around from the 318 i junked. my 1970 has a 273.

Making sure everything is leak free is paramount in impeller performance. People shred stuff all the time and I have no clue how.

I use just a little cheap dish soap sometimes if it is available. Otherwise I just put water in it. I dry start before I go to the ramp just long enough to hear it fire. I drive my stuff like I stole it and I get about 3 seasons or 260-350 ish hours out of the G21 impellers.

My trigger to replace is when the temp starts to creep up a little at idle after a long BF run and takes a while to come down.

Not so much the wear but the rubber compound gets soft and squishy and reduces pumping efficiency.

(edit) I also remove belts/hoses during winterization and turn the impeller backwards to remove any water in it. Leave it that way till spring and turn it by hand to make sure it isn't stuck to the housing an rips a blade off like I've seen so many times.

8122pbrainard wrote: GMacLaren wrote: I've seen ads for impellers that will run "15 minutes dry" and wonder if they are rubber. They are a urethane compound instead of a Buna-N.

A friend here looked at my new Sherwood impeller and said he doesn't think it's rubber. (He's the once-owner of the once largest boat dealer here in STL and has rebuilt many boat engines. He's retired now, but still restores outboards -- he's rebuilt hundreds.) He thinks the material is a sophisticated compound devised especially for the pump impeller application.

BTW, Sherwood has a nice PDF of their 2009-10 manual on the 'net. They sure make many models.    

I am really learning as I go. Sound to me like you are really ready for a pump rebuild -- maybe only an impeller. But I'd suggest you do it NOW; don't put it off. With a good pump, you won't have to "check for prime." If you see water at the exhaust very shortly after engine start, ypu'll be good to go.

Found on page 11 of the Sherwood Pump manual:

8122pbrainard wrote: baitkiller wrote: a well maintained pump and plumbed system will not require priming. These are not flooded suction pumps. Correct a flex impeller pump is self priming but, if there is a air leak or say a hose not connected after winterizing preventing priming, it doesn't take long to heat up from lack of lubrication. The rubber quickly deteriorates and breaks up from heat.

baitkiller wrote: 14 years on an impeller is not something to boast about.

Did you read the original thread? It was not boasting but rather stated fact. It was mentioned due to the belief that impellers need to be replaced every year. That is what's absurd!

This is the only reason to use a non petroleum based lubricant:

JoeinNY wrote:    On the less self inflicted side if you have a slight air leak or blockage and the system doesn't prime right away having lubed the impeller will keep you from smoking it before you figure out the source of your troubles.

I used to review test results for rubber parts, they test against heat, aging, UV, ozone, oil, & compression set, but not alkali resistance. I think dawn is a safe bet.

Ozone is one of rubber's worst enemies. If you remove it during layup, put it in a ziplock bag, out of the sunlight & it will last much longer.

In our group of ski friends with many tournament boats and 30+ years boating together it seems we usually get a small warning. The engine starts to run a little warmer at idle not long before it goes out.
Usually temps are normal running but hotter at idle. Heed the warnings, I don't think you get 1 more hour use after the temp fluctuates before you are stranded with no pump at all. I am an every other year replacer now.

And I've gone (as Tim remembered from a previous post) 14 years on impellers (dual cavity on my 312). It too lives in a boathouse in northern Wisconsin. Yours is a classic case of running dry. Even if you or your friend drops it in the water before starting, does he check to see if the RWP is primed?

This is absurd and an anomaly. 14 years on an impeller is not something to boast about.
In addition I will add that a well maintained pump and plumbed system will not require priming. These are not flooded suction pumps.
You want a rule-of-thumb? How about the third year is borrowed time.