RWP priming question - '87 SN 2001

I don't think I missed the point. I just worded my point poorly.
What I was trying to say, is that with a fake a lake, there is no direct hose connection from the house to the boat. Therefore house pressure could not transfer through the motor. Perhaps with a T line it could, but I don't think that the way a impeller is designed that much house pressure would bleed through anyway to mask a poor impeller. Unless of course the impeller was shot and did not form a tight seal inside the housing.
I could be wrong on that.....but that is what I was trying to say.

We're on the same page. That's why I said its fine for a quick engine test or warm up.

I think you missed the point corey. Its not about the impellor taking more pressure, although I'm not sure what that means. The point is, if you run on a hose, the hose can push the water though the engine. It can mask a situation where the pump is turning but not pulling any water, so you think its fine in the driveway and you get to the lake and you over heat. Pumps can turn, but if there is the least little bit of an air leak between the pump and the lake, you will not get any, or at least enough water. Many here, including me, have seen this. Running on a hose (or plunger) is fine for a quick engine test or warm up in the driveway, but it is not the way to go to verify that your pump is good.

Pete, I could be wrong but I think a Timmy-T is fine for testing a RWP. I think the easiest path for the water to follow is out the thru-hull and that is would take "full suction" to divert the flow to the engine. But I could be wrong, maybe pulling from a Timmy-T takes less than perfect suction. That, I don't know. Bucket's the best, I guess.

Sincerely appreciate everyone's input.   I guess my general take-away is that most likely I won't need to prime, but the possibility of the flush technique being used could end up masking some RWP problems due to positive water pressure being created by the hose.

Taking all factors into consideration, I see that Larry and Pete both allude to the fact that the preferable method would be just using a bucket full of water on the input side.

This makes perfect sense to me.   It ensures that the RWP is producing enough draw for ample cooling and isn't suffering from any air leaks or other issues that may masked due to the positive water pressure. Kinda killing two stones with one bird...

Many thanks!

Rob,
Unless your Chris was pre WWII, you should of had a rubber impeller RWP which shouldn't need priming. Something was wrong. If pre WWII, then gear pumps were still used on some engines but they would have grease cups that would be screwed in to pack the gears to prime with grease. The Timmy T or the Fake-A-lake plunger methods both can hide RWP problems with pressure from the hose.

A factor in what?

Doesn't need priming. Fire it up. Just make sure its pumping water and not just running on water pressure from a hose. So either in the lake or with the water intake hose drawing out of a bucket is the best assurance that its pumping.