Merc HP500 (502) Water Pump Help Needed

pugracer285 · 04-08-2010, 10:10 PM

Hi All,

I launched off our Extreme for the first time today since we picked it up a couple of week ago. We saw it running on the trailer with a hose adaptor stuck up the raw water intake (mounted on the transom) and there was plenty of water coming out of the exhausts.

When I fired her up today after launching there was no water coming out of the exhausts. I ran it for probably 90 secounds as I wasn't sure whether it took a while to come through. During this time I looked into the water strainer and there seemed to be bubbles indicating flow, the impellor housing didn't feel particularly hot. Having then switched it off and been through the cooling system (eventually removing the impellor housing) looks like it's eaten itself.

Couple of questions....

1. Where am I likely to be able to source a new impellor/gasket kit from in the Southampton/Warsash area and what am I asking for (as there are no part numbers on the old one) also does anyone have any recommendations as to a preferred make?

2. Did I do something obviously wrong? Is it possible for an airlock to happen between the raw water intake and the impellor housing or should the impellor suck the water straight up through the filter without any priming?

If the answer is yes, as I only had the engine on idle, should I have revved it up a bit to create more suction when first started?

Apologies for the niavety but this is my first V8, only ever had outboards with integrated leg impellors before!

Thanks
James

neal_skyline · 04-08-2010, 10:24 PM

bursledon outboards opposit decons boat yard ,they keep them in stock

DiamondPerformance · 04-08-2010, 10:39 PM

You have the two piece housing, the one piece housing is easier to work with.
46-807151A14

pugracer285 · 04-08-2010, 11:29 PM

Thanks guys I will try Bursledon in the morning. Any ideas on the air lock theory or is it just likely to be down to an old impellor not pulling the water through?

DiamondPerformance · 04-08-2010, 11:33 PM

Looks like an old housing and impeller. The impellers take a "set" when they sit too long.

larby · 05-08-2010, 12:32 PM

Before you fit a new impeller and carry on, besure to flush the system through backwards as well as possible! It looks like you were lucky, buit if any bits of impeller got through into the engine they could be lodged somewhere and causing a restriction or blockage!

James

pugracer285 · 06-08-2010, 07:40 PM

Hi All,

Thanks for the help thus far. I managed to get an impellor kit from Marine Power and fitted it without too many issues.

(yes I'd already back flushed the system which brought out the 2 other missing broken impellor blades which must have been down in the oil cooler!)

Next issue is the main circulation pump now seems to be making a horrible squeaking noise when run under load. I've had the alternator off to be tested as we thought it was this but nothing wrong with it.

I am therefore now in need of a big block circulation pump if anyone has one. I'll try Marine Power in the morning but would rather give someone on here the business if they can sort one at short notice.

The joys of new boat ownership.... this was supposedly a minter...ha the list of faults is growing by the hour!

James

ps. Larby my floor is a bit "spongy" let's hope I don't get tempted to do a little "remedial" work and end up like your Revenger!

DiamondPerformance · 06-08-2010, 07:44 PM

Your seawater pump also has oil in it to cool and lube the bearings, check it.

pugracer285 · 06-08-2010, 07:56 PM

Thanks for the quick answer, excuse the ignorance but how do I check it? (back home now so can't look until the morning)

Does it have external pipework plumbing it into the oil system or are there some oilways linking through the mounting flange where it bolts onto the block?

The boat lives on a dry stack so I had it pulled out this afternoon, can I check it without running up the engine as I'm a bit wary after the previous impellor problems.

DiamondPerformance · 06-08-2010, 08:03 PM

It has a oil bath in the pump, in your first photo, there is a screw in front of the impeller housing, this is the oil fill. It's easier to remove the pump from the motor to check the oil. Use drive oil to fill.

larby · 07-08-2010, 09:03 AM

You can have my circulation pump if you like, I'm fitting a crossover or whatever it's called with the blower. PM me your address and I'll pop it in the post...

Cheers, James

pugracer285 · 10-08-2010, 10:46 AM

Hi Larby,

Thanks for the offer but it's the large water circulation pump that I need which bolts onto the front of the block behind the pulleys. I'm trying to source one from Barrus but not currently having much luck!

larby · 10-08-2010, 11:31 PM

Yeah I know,that's the one I'm offering!...

Sheesh, can't even give it away!

James