4hp Mercury outboard impeller, how do I remove it!? :S

Ballistix

Ballistix

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www.cinematreadwell.com
Hi peeps,

Father in law decided it was time to change the impeller, after 20 years. He could tell something was wrong due to over heating, twice, in the solent...ahem..it's quite an old "40" 4hp merc, blue letters, metal top. But in good condition it appears.

Anyway, photo below, how the devil to I get it off? Does the shaft have to come out?! Cheers in advance!
Regards,
Tony

Dscf2690.jpg
 
Re: 4hp Mercury outboar impeller, how I remove it!? :S

hi, under the black rubber is a brass sleve,use a sharp chisel and hold parell to the shaft, tap down on the brass sleve to split it open ,it shood then just slide up of the shaft,if it is to hard to split, drill in from the side with a 3/32 drill in as far as the shaft to weaken the sleve first.
 
Youv'e taken the top off the pump. In theory it should now be possible to yank the impeller out of the pump body (watch out for the key though) but I guess its well and truly stuck to the shaft by now. Long long overdue for a change!

As far as I can see if necessary it should be possible to remove the pump body together with a whole host of shims, bearings, seals O rings etc together with the shaft but really the impeller should come out next.
Don't know though what will be required to get the bearings out. The shaft wont pull out on its own as the pinion gear on the bottom will stop it.

You dont say exactly what year it is or what the engine number is so cannot be sure to be looking at the right pictures. However you'll find exploded diagrams at

http://www.crowleymarine.com/parts.cfm

Quite useful but not a substitute for a manual.

Replace any seals and O rings you may disturb. You wont want to pull it all apart again because its letting water into the gearcase.

If all else fails ask for advice on the Mercury/Mariner board on the iboats forums If you do though quote the full engine details, at least year or model/serial number.
 
Hi, great info thanks. It's a serial number starting in 31 something and that Crowley site has a picture of the the exploded view. It seems like it should just come off but I think, as you can see from the picture, it's been on there a while and the shim has probably coroded I'll give it some more pressure tomorrow.

Cheers

T
 
ps dont forget all the missing parts from the old impeller have had to go through the water system,place a garden hose on the outlet and flush the system through before re-asembly,if there is a dark line around the steel insert it has over heated and may be out of true,i would fit a new base-impeller-and top
 
Also, thought I'd better check mine, 2001 4HP two stroke Mercury. I can't even get the bottom of the leg off, different mechanism? It's being stopped somehow by the gear change mechanism?

STOP. Found it, under a gromit, small nut to release.

T
 
[ QUOTE ]
When you say base impeller and top

[/ QUOTE ] I think he means the housing , the impeller and the cover.

I think you'll find the housing has a metal insert and that there is a metal plate in the cover. They may well be worn.

If in any doubt about the overall condition of the pump it would perhaps be wise to get a pump repair kit. That should contain all the bits you are likely to need. If there's one available it'll be on the parts list.

By the way when installing the new impeller twist it in a clockwise direction as you ease it into position so that all the vanes are pointing in the correct direction.
 
Hi all. Well I got it off, after a chisel was used! Anyway, after a lot of messing around and cleaning up I've got the new one on. However, on running, I'm not seeing any water exiting the top of the engine. Now because this is an old 40 4hp from Merc I'm not sure I should...

On closer inspection I think it should be coming out of a little plastic pipe underneath the head encloser. The exhaust is coming out of a larger hole at the back of the head case. I took off the pipe and the little plastic piece that is screwed to inside the head and it was full of muck and grease so I blew that out and cleared it...now all I see coming from that little hole is exhaust! Along with the large hole at the back.

Is it possible I didn't like up the tube in with the impeller housing and I've missed it and put the thing together and that's why I'm seeing exhaust fumes out of there? I can also see exhaust fumes/smoke coming out of the propeller (under the water) and I'm guessing this is because exhaust is being forced out through the impeller channel??

Any ideas?

STOP: Fixed it...didn't have the water pipe hooked up to the outlet properly it slid down the side...

Cheers
T
 
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