Aux water pump

[BogMonster]

I have a Mariner/Merc 4hp as an aux, that I got just after the boat, so late 2010.

It gets exercised semi-regularly to make sure it still works, but has probably only accumulated less than 10 hours total run time.

What's the view of the need or otherwise to change the impeller? I haven't done the main engine yet (just ordering the bits now) and that's six years old but obviously has many more running hours.

Thoughts please? How big a job is it on the little motors anyway - I assume it's in the gearcase same as with bigger motors, and so a fair bit of disassembly will be required?

[jeffstevens763@g]

Rubber work hardens and with age for the cost I would drop the lower leg and fit a new impeller cheers

[Nos4r2]

Change it.You're risking shedding vanes from the impeller. Does it have forward/reverse?

[Poly]

Originally Posted by jeffstevens763@g

Rubber work hardens and with age for the cost I would drop the lower leg and fit a new impeller cheers

I think technically it just hardens with age rather than work hardening (hence even if not working it still hardens).

Bogmonster - even if the impellor itself is in fine shape, it won't do any harm to remove the lower leg and regressed all the bits (so you might as well replace the impellor) otherwise when it does eventually need doing you have the joy of all those seized bolts etc. to contend with.

[willk]

Originally Posted by BogMonster

Thoughts please? How big a job is it on the little motors anyway - I assume it's in the gearcase same as with bigger motors, and so a fair bit of disassembly will be required?

They're not in the gear case but above it. The job is simple and should be done - if only to ensure bolts aren't seizing up.

Order the full works - impeller, woodruff key, two gaskets and the seals for the gearbox oil screws and get that oil changed too!

[jeffstevens763@g]

Originally Posted by Poly

I think technically it just hardens with age rather than work hardening (hence even if not working it still hardens).

Bogmonster - even if the impellor itself is in fine shape, it won't do any harm to remove the lower leg and regressed all the bits (so you might as well replace the impellor) otherwise when it does eventually need doing you have the joy of all those seized bolts etc. to contend with.

The vanes don't return to vertical after a while they stay facing backwards loosing their spring in effect work harden because they are under pressure all the time then go brittle that's when the problems start with bits in the water ways impellers are part of the service kit so should be changed in line with service intervals

Cheers

[Bern Hanreck]

I think Nos asked a very pertinent question ! ( ie does it still have forward and reverse ? ) .

I used to run my auxillary as a precaution , always flush and occasionally service but the gear selection mechanism seized solid in neutral . Required a strip down to rectify . Well worth exercising and lubing.....

[BogMonster]

Yes - everything still works and gets exercised to make sure! Pottering around with dolphins is a good way to work the aux for a bit. I sometimes do the "Hey look I've got twins" thing and put the aux full ahead and the main slow astern to do 360s

Gear selection was a bit sticky around year 2 but was sorted out and is now fine. The only other issue I had was some dirty fuel which blocked the carb (on a test run), but I now take the whole internal tank out annually, empty it right out, swill it around with some clean fuel and refill with fresh to prevent a reoccurrence.

All comments noted, the problem here is needing to make ABSOLUTELY sure you've got everything to hand before pulling it to bits as it takes weeks to get anythng missing down from UK. I'm currently going through that process to get all the bits for the main engine and if I get that job behind me with no problems then I'll turn to the aux.

Thanks.