Engine hot after impeller change?

[BaitThrower]

Decided to pull the leg on my second hand 15hp outboard for the first time today to check the condition of impeller. Was pumping ok but wanted to check it anyway and replace so at least I knew when it had been done last.

Anyway put on new impeller and assembled everything back together, but after test run, engine block seems A LOT hotter than before. Before I could put a finger on it for 4-5 seconds and only be warm, now I touch it and burn my finger if not careful!

Water is pumping still with new impeller but doesn't seem as strong a flow... perhaps less pressure. Any ideas? Its an '86 Jonhson.

[FNQCairns]

No good ideas apart from pull the leg again and repeat the exercise but take 3 beers to do instead of two, the sooner the better and certainly before you start it again.

Did you compare both the old and the new impeller side by side before fitting?

good luck

cheers fnq

[BaitThrower]

Pulled it three times! Checked and double checked. Yep compared impellers, they appear the same. Just wondering if the new one may take 10-15 minutes to seat properly or conform to the pump chamber? Tomorrow I'll get the compressor out and blow out the cooling passages too. Maybe some crap has built up in there recently.

[Spaniard_King]

did you use a gasket sealer on the O-ring on the pump housing.. they tend to warp a bit and are hard to get to seal if a new o-ring is not used!

[Roughasguts]

So that there little tube that has a rubber gromett and comes from your water pump and goes to the engine block. Is the tube in place properly ? is the rubber sitting right? or is it missing ? Cause if it's any of those you will have less cooling pressure.

[tigermullet]

Could the impeller be slipping? This might sound really stupid but you didn't lose the D shaped thingy did you?

D shaped thingy is the technical term - I don't have any idea what its common name might be.;D

[Roughasguts]

Could the impeller be slipping? This might sound really stupid but you didn't lose the D shaped thingy did you?

D shaped thingy is the technical term - I don't have any idea what its common name might be.;D

That be the woodroofe key.

[tigermullet]

So that there little tube that has a rubber gromett and comes from your water pump and goes to the engine block. Is the tube in place properly ? is the rubber sitting right? or is it missing ? Cause if it's any of those you will have less cooling pressure.

That could be it! Just remembered - the same thing happened to a little motor of mine. The mechanic didn't line it up properly when putting everything back together - the grommet was distorted and pushed down into the housing.

[BaitThrower]

So that there little tube that has a rubber gromett and comes from your water pump and goes to the engine block. Is the tube in place properly ? is the rubber sitting right? or is it missing ? Cause if it's any of those you will have less cooling pressure.

As far as I know it was inserted right. I made sure I lined it up when putting the leg back on anyway.

[BaitThrower]

did you use a gasket sealer on the O-ring on the pump housing.. they tend to warp a bit and are hard to get to seal if a new o-ring is not used!

I used a new o-ring from a new kit.

[BaitThrower]

Could the impeller be slipping? This might sound really stupid but you didn't lose the D shaped thingy did you?

D shaped thingy is the technical term - I don't have any idea what its common name might be.;D

Not sure what you mean but I inserted the little pin which drives the impeller around and made sure it was spinning as I rotated the drive shaft.

[BaitThrower]

Question... are you supposed to use anything on the underside of the bottom plate of the fuel pump? The lower plate the impeller sits on/rides against?

[tigermullet]

I'm out of ideas. What brand of motor is it?

As far as I know it is not necessary to put anything under the bottom plate of the pump. The impeller just slides up the shaft (after removing the upper side of the pump housing) The new impeller slides down and is held by the key (or, I guess, pin), new rubber grommet etc.. and do up the bolts.

Seeing as you seem to have done all of that and got a proper line-up with the tube I cannot think of anything else that might have gone wrong.

[tigermullet]

Sorry - re-read your first post and had missed the engine type on the first read.

[Spaniard_King]

did you use a gasket sealer on the O-ring on the pump housing.. they tend to warp a bit and are hard to get to seal if a new o-ring is not used!

If you have it all right then its the o-ring not sealing on the plate::)

[tunaticer]

My guess is the copper pipe has taken a chunk out of the rubber grommet up under the motor and that chunk is sitting in the motor somewhere reducing the flow. Once that rubber grommet is damaged it also leaks water back down the inside of the leg and out the exhaust plus deliver lesser quantities of water to the motor.
You might be able to black flush the piece of rubber grommet with the leg removed by putting the hose into the fitting where the telltale comes out.

Jack.

[Roughasguts]

Question... are you supposed to use anything on the underside of the bottom plate of the fuel pump? The lower plate the impeller sits on/rides against?

Is that plate really badly scored ?
You could use rubber grease but that would only last 2.5 seconds.

Think I would put the old impellor back in, and see what it does.

If it still gets hot then it ain't the impellor, it's one of the other things mentioned.
Cheers.

[dreemon]

does the motor have a thermastat?

[CHAPPY]

my 2002 15hp johno has just had the impella changed and the technician put a temp tester on the housing and was looking for 37 degrease as optimal. after about 2 min.

hope this helps
Chappy

[Kleyny]

Just a thought, you havent put the impellor fins the wrong way?
Father in law done that to his, it pumped water but not much then it chewed out after about 20min trip.

neil

[Imfiik]

evinrude and jonnos used to have a problem with the o ring where the water tube fits into the powerhead up top. It distorts and blocks off water flow , has killed quite a few motors. Not easy to get to but that is why it is often overlooked.

[BaitThrower]

Thanks for the suggestions. I might pull the leg off again and run the hose intot he copper tube and somehow ghet the O-Ring to seal but thats almost impossible to tell because its out of view by the time you get the leg back on and pushed up.

One other thing. I ran some kind of detergent flush through it a week or two back (Ya, prolly dumb thing to do - will be water only from now on). I run in a bucket so a lot fo the oily water gets sucked back up and this oil probably coats the internal cooling passages. Is it possible the detergent cleaned this all off and its getting hotter because the lack of oil coating in the cooling passages?

Im just running it at idle for a minute at a time at present to ensure it doesn't overheat and between each run, blasting compressed air up the peehole. This seems to be finding its way back down to the cooling water exhaust ok so maybe she just needs some nice oily water run through it again. The pump seems to be gaining a little more pressure and better flow out the teeltale too. Perhaps the new impeller is seating itself better now too and closing off any gaps in the pump chamber.

[Roughasguts]

Mate if your only idling it for a minute thats probably not enough water pressure, and it won't bed in the new impellor either.

Give her some rev's next time they also run cooler with rev's and no load.

[spears]

Your kit should have looked like this,is this what you bought:

[BaitThrower]

Mate if your only idling it for a minute thats probably not enough water pressure, and it won't bed in the new impellor either.

Give her some rev's next time they also run cooler with rev's and no load.

So rev it a bit with no gear engaged?
I thought this was a no-no?
It's getting so hot so quickly, that I dont want to damage it by revving it too much. I think the impeller etc is working all ok coz its pumping water to the tell tale at about 80% full strength (at a guess) so I'm thinking restricted flow around head might be problem now.

[BM]

Bait,

Take off the leg and run the engine with the garden hose on the water tube (that runs up to the powerhead). If it runs cool then the problem is your pump. If it still runs hot the problem is in the powerhead somewhere.

Do that first as it will direct you to the problem area in a matter of minutes.

Oil coatings on engine blocks is mythical stuff and won't help cool it down nor will it protect it from salt.

Cheers

[BaitThrower]

Bait,

Take off the leg and run the engine with the garden hose on the water tube (that runs up to the powerhead). If it runs cool then the problem is your pump. If it still runs hot the problem is in the powerhead somewhere.

Do that first as it will direct you to the problem area in a matter of minutes.

Oil coatings on engine blocks is mythical stuff and won't help cool it down nor will it protect it from salt.

Cheers

Thanks mate I will try this. id id this very thing yesterday with the hose on the copper pipe but not with the engine running. so might try it again with engine running.

[BaitThrower]

Another quick Q... is the copper tube that takes up the water from the pump supposed to have a little bit of play in it? This one you can wiggle around slightly. It is not firmly fixed it seems... normal? or not?

[BM]

It sits in a rubber grommet at the powerhead end so yes there is normally a bit of flex. When the leg goes back on it all gets held firmly.

Cheers

[BaitThrower]

ok thanks :)

[jimbo59]

When mounting the new impellor did you turn the drive shaft clockwise as you lowered the housing?