Mariner 2.5 impeller

[Daydreamer]

Old Mariner 2.5 HP outboard runs easily but doesn't seem to pump cooling water. Obviously suspect the impeller.

The exploded parts diagram suggests that the impeller is in the leg rather than behind the prop.The bolts holding the gearbox to the leg come out easily
and the gearbox is clearly free to move but won't come off. The diagram seems to show that there is a circlip at the end of the main vertical driveshaft.

Can anybody please confirm that this the case and suggest how to get to the circlip (although I think I can guess )

 

[Rigger Mortice]

Before you worry about the impellor, check that the tell tale isn't blocked. Poke a few inches of soft wire (I find solder does the job) up the rubber pipe. Prod around for a minute, then try the engine. Pound to a penny that will solve it.

 

[monkfish24]

Old Mariner 2.5 HP outboard runs easily but doesn't seem to pump cooling water. Obviously suspect the impeller.

The exploded parts diagram suggests that the impeller is in the leg rather than behind the prop.The bolts holding the gearbox to the leg come out easily
and the gearbox is clearly free to move but won't come off. The diagram seems to show that there is a circlip at the end of the main vertical driveshaft.

Can anybody please confirm that this the case and suggest how to get to the circlip (although I think I can guess )

there should be two bolts, one fwd of the leg and facing up, the other just under the cavitation plate. If both of those are off, it might just take a thump to get the shaft cover tube to release it's grip from the big end seal.

 

[awol]

Yup, if your model is the same as mine, there is a circlip. Prop off, 2 bolts (best to drain the oil first!), pull off the cover and pop the circlip with a small screwdriver/whatever. Much more fun to put it back. There is a kit for about £40 that includes the impeller, new pump chamber and all the seals.
My impeller had half a blade left!

 

[Lakesailor]

You must drain the oil.

 

[greenalien]

A word of caution - the outlet pipe from the pump can sieze in the pump housing, and may break at the top end, where it goes into the head, when you pull the bottom end off. Worth trying to get as much WD40 as you can manage into the area in and around the pump first, and leave it for a few days.

 

[Daydreamer]

Yup, if your model is the same as mine, there is a circlip. Prop off, 2 bolts (best to drain the oil first!), pull off the cover and pop the circlip with a small screwdriver/whatever. Much more fun to put it back. There is a kit for about £40 that includes the impeller, new pump chamber and all the seals.
My impeller had half a blade left!

Yes. Exactly as you say. Thanks.

It is I think, this(gearhousing assembly) very early model.

Incidentally can anybody tell me a spec. for the oil. It smells like standard gearbox oil to me.

 

[awol]

Yes. Exactly as you say. Thanks.

It is I think, this(gearhousing assembly) very early model.

Looks just like mine - so ignore Lakesailor's "You shouldn't need to drain the oil." unless you want a puddle on the floor; the water pipe is simply pushed into a rubber grommet though it is an almost blind mate on reassembly; the Yamaha kit I got had the grommet and parts 12 thru' 16 included + the screws #20.

I refilled mine with EP90, 'cos that's what I had on the shelf - I don't imagine it is very critical.

Incidentally, wheelie bins make a good test tank and it washes the bin as well if you add detergent to kill the oil film - one of the few boaty things that actually earned me brownie points!

 

[Daydreamer]

A word of caution - the outlet pipe from the pump can sieze in the pump housing, and may break at the top end, where it goes into the head, when you pull the bottom end off. Worth trying to get as much WD40 as you can manage into the area in and around the pump first, and leave it for a few days.

Oil drained and circlip popped, housing is 'free' but won't slide off. Have I met the seized water pipe do you think?

I'll know how to do it when I've done it!

 

[VicS]

Incidentally can anybody tell me a spec. for the oil. It smells like standard gearbox oil to me

Any high viscosity ( around SAE80W-90 ) outboard gear oil.

Automotive EP 90 oil gear does not contain the inhibitors that protect against the effect of water ingress other wise will do.

If the old oil was not clear and bright but cloudy due to water now is the time to also replace the seals.

Oil drained and circlip popped, housing is 'free' but won't slide off. Have I met the seized water pipe do you think?

I think it is more likely that the drive shaft is stuck on the crankshaft.
The waterpump impeller prevents the drive shaft pulling out of the pump assembly but once you have freed it from the crankshaft you can unbolt the pump assembly and lift it away complete with driveshaft.

PITA having to release the circlip on the bottom as well!

Rebadged Yamaha engine I think.

 

[awol]

Oil drained and circlip popped, housing is 'free' but won't slide off. Have I met the seized water pipe do you think?

I'll know how to do it when I've done it!

The drive shaft is just a tube with a squared end which pushes on to the crankshaft - it can't come out the pump 'cos there's a drive pin through it for the impeller. I seem to remember getting to this point and applying a bit of brute force. The water pipe simply slides into its seal - I can't see it as a problem.

 

[Daydreamer]

Have I understood this correctly?

The pump unit is in the gearhousing and the driveshaft should pull out of the crankshaft and all of this should come out in one piece. So in fact it would be better if the circlip were left in place until the drive shaft is pulled out. Its clear the the D/S is trying to pull out of the pinion at the moment under the fairly gentle pressure I am applying.

Brute force will have to wait until tomorrow.

Thanks for all your help.

 

[VicS]

Have I understood this correctly?

The pump unit is in the gearhousing and the driveshaft should pull out of the crankshaft and all of this should come out in one piece. So in fact it would be better if the circlip were left in place until the drive shaft is pulled out. Its clear the the D/S is trying to pull out of the pinion at the moment under the fairly gentle pressure I am applying.

Brute force will have to wait until tomorrow.

Thanks for all your help.

The pump cover is bolted to the top of the gearcase.

The impeller is pinned or keyed to the shaft inside the pump housing

Yes IMHO the circlip would be better left in position until the drive shaft is separated from the crank shaft. It will take all the force that is necessary to get them apart. With it off all the force is being taken by the water pump impeller and cover, which you might damage and is apparently now obsolete

 

[awol]

My memory is that I had removed the circlip and that gave sufficient space to lever at the flanges but then I was flying completely blind. I do concur that leaving the circlip in place is probably better. Have you sourced the repair kit yet?

 

[greenalien]

The water pipe simply slides into its seal - I can't see it as a problem.

That's what it's supposed to do, but if the motor wasn't regularly dismantled (annual service is supposed to include checking the impeller!) the copper pipe has a tendancy to corrode over time, locking it into the seal. If you're lucky, it'll pull out; if not, it may pull cleanly out of the head, complete with the head seal, or it may break on the top bend. Been there, done that...

 

[Lakesailor]

Yep. It's old.

Expect collateral damage.

 

[Daydreamer]

That's what it's supposed to do, but if the motor wasn't regularly dismantled (annual service is supposed to include checking the impeller!) the copper pipe has a tendancy to corrode over time, locking it into the seal. If you're lucky, it'll pull out; if not, it may pull cleanly out of the head, complete with the head seal, or it may break on the top bend. Been there, done that...

Exactly what happened! But it would seem to be inevitable, even when it was all apart it took a lot of effort to remove the pipe from the rubber seal. Part of the problem appears to be a build up of hard scale on the end of the pipe.

 

[Daydreamer]

Continued.

But what to do, the water pipe looks repairable but presumably I will need to remove the leg from the the crankcase to refit it but I wonder what I am going to find there. It looks unlikely that I will get gaskets etc.

I am reluctant to scrap it because it is a very nicely made item and in remarkably good condition for its age but it is I suppose beyond economic repair.

 

[Lakesailor]

It's copper pipe. Make a spacer from some bigger pipe and solder it in leaving some fresh, correct size pipe to go into the seal.

 

[greenalien]

After I broke mine, I realised that it wasn't going to be a quick fix, so I put the motor away with the intention of fixing it later, bit the bullet and bought a new one. (it was the middle of the sailing season, and I preferred being afloat to trying to fix an old motor).After a couple of years, I remembered that it was still in the garage, realised I was never going to get round to fixing it, and put it on Ebay, where it found a new owner who enjoys fixing outboards.

This decision was aided by the fact that I remembered that it had had some as-yet undiagnosed cooling problem which was almost certainly blocked cooling passages in the head, and that I reckoned the chances of getting the head apart without shearing the bolts was zero.