77 merc 500 water pump issues

[greasemonkeyjmj]

i have a 77 nerc 500 that has been sitting since 1992. i did some rewiring and carb work and it seems to be running good. but my concern is that, the tell tale only put out a stream of water about 4 to 5 inches long, even at high idle. i have installed a new impeller, everything in the pump housing area looks good. i pulled all of the old rubber out that i could find and even pulled the water pickup screens and cleaned out the bits.i blew compressed air through the telltale hose and it sounded as if it was open with no blockages.due to transom problems with the boat, i havent ran the motor in the water, only on muffs.i seem to have a good flow of water out the prop hub, there is none out of the ports below the cowling. also there is water coming out of the holes right above the cavitation plate, above and to the front of the trim tab. is this normal ?

 

[emckelvy]

Re: 77 merc 500 water pump issues

James, hopefully none of the chunks of rubber made it up into the water tube and/or powerhead! There was a very long thread here a couple of months or so ago about a Merc running warm-ish, and it turned out that at piece of impeller blade lodged itself up towards the top of the water tube and was acting like a restrictor!

It does sound like you've got a fair amount of water flowing thru the motor at idle, at least. Getting a goodly amount of warmer water out the prop hub is a good sign. When you're running on the flusher, make sure you turn the water pressure up enough so that some water spills out the muffs. This ensures the suction side of the pump is fully flooded and you'll get the best pressure to the powerhead you're gonna get while on muffs.

Proof of the pudding is taking 'er out in the water, guess that's gonna be a while, eh?

Lay your hand on the exhaust manifold while running, and it should be cool. If it's getting very warm you have circulation problems. You may want to pull the lower unit off and check the water tube for restrictions or even hook up water to the tube and see if you get a stronger telltale.

Otherwise I'd check it real closely when you first light it off in the water and see what she does.

Cheers & Have Fun with that Transom! Can you say, 'Seacast', I knew you could!!!!..........ed