Johnson 115 water pump impeller

BogMonster · 22 March 2006, 13:08

I have just had somebody asking about my new acquisition, wanting to know if the water pump impeller was OK or had been changed recently, but wouldn't tell me why!

Is there a known problem with water pump impellers on this particular type of engine (Johnson 115hp 2 stroke V4, built in 2000)?? I have just done a search both on here and Google but nothing came up.

The guy who said it was the owner of the boat I didn't buy so I figure it is possible he is just winding me up but thought I had better check...

I have a new impeller in the box of bits that came with the boat anyway, and as they presumably don't last forever I don't suppose it is too hard to change, though I haven't looked in the workshop manual yet (because it's at home and I am at work)

Thanks

Stephen

ADS · 22 March 2006, 13:28

Stephen,

it is good practise to change the water pump impeller as part of an annual service. With a knackered impeller the engine will over heat and the (tell tale) stream of cooling water exiting under the cowling will be minimal. There is an excellent thread here by Richard B with step by step photos on changing an impeller:

http://www.rib.net/forum/showthread....light=impeller

If you have problems getting parts I have a large Johnson dealer near me South Coast Marine and I would be happy to pick you one up if you organised the postage.

Alex

BogMonster · 22 March 2006, 13:44

It sounds from talking to somebody else (who knows both previous owners) that this one may be way overdue for being changed and possibly even still the original one, but the tell tale was fine when we went for a test run. I think I will do it sooner rather than later to be safe, a spare one came with the boat anyway, though reading that excellent thread suggests that rather more might be required than just the impeller. The spark plugs have also been in there for rather longer than they ought to have been by the look of them! Still I have a full workshop manual so I have all winter to fiddle with things

So you don't know of any "known problems" with impeller failure on this particular type of engine?

Thanks for the offer re. bits, might take you up on that

the engine etc came from Oakley Marine but as they still haven't bothered answering an email I sent them a couple of weeks ago I can see I am going to fall out with them real quick...

ADS · 22 March 2006, 14:16

Quote:

Originally Posted by BogMonster

So you don't know of any "known problems" with impeller failure on this particular type of engine?

Not in particular, they can fail on any outboard, I was always told to change it every season regardless of whether it needed it. However, I do know people who have never changed the impeller or serviced the engine, and whilst it runs I doubt it is giving its full potential. Sounds like your engine is due for a bit of a service, with a manual should be no problem to do it yourself. This would make a gd discussion point, what constitutes a full service on a 2stroke carb outboard??
In my opinion
-plugs
-impeller
-gearbox oil change
?????

-R.E picking up parts no problem.

Alex

BogMonster · 22 March 2006, 15:10

Yes I was thinking the three things you mention would be done sooner rather than later so I know what condition they are in.

I have since spoken to the guy I bought it from who said he has never had to change it in 3 years, so there can't be a problem with them failing but on the other hand sounds like it is overdue!

Nos4r2 · 24 March 2006, 00:45

Quote:

Originally Posted by ADS

This would make a gd discussion point, what constitutes a full service on a 2stroke carb outboard??
In my opinion
-plugs
-impeller
-gearbox oil change
?????

Alex

Clean floatbowls out.

Decoke with redex(I use a bottle in a 25 litre tank of premix).A lot of the Yanks on iboats.com do this as a matter of course as part of dewinterising.

Change fuel filters/drain and clean water traps (and tanks if possible)

My tanks get a bit of winns dryfuel sloshed around in them with about a pint of old fuel to clear any water.

If your boat has been a bit neglected (and it sounds like it if it's still got the original impeller in the engine!) I'd do all of the above.

Cleaning the floatbowls would be a good idea before running redex through-
redex is so good at clearing crap out of carbs that it can lift big flakes of stuck in crap from the floatbowls.I once ended up limping home on 2/4 cyls after exactly that happened and the crap ended up in a mainjet.

Alice · 24 March 2006, 08:43

Definitely a good idea to change the impellor on a newly aquired engine. I'm not so sure that it is absolutely necessary to change every year whils't in one's ownership. I've replaced every year and the one I was chucking was perfect. The big no no is to run them dry. It knackers the thing in seconds. Marks and groves on the impellor housing are a sign that it little trauma has occured in there.

BogMonster · 24 March 2006, 10:14

Thanks ... I'm definitely going to do it sooner rather than later, just to be sure, and the gearbox oil etc as well. A couple of hours on the water on Wednesday showed no problems though - but there is one irritating thing which is the angle of the tell-tale, it is pointing downwards so you can't see it at any speed, you have to slow right down to be able to see it which is a PITA. Better if it can be set to point straight up in the air I think, so that's on the "fiddle with on the weekend list"...

BogMonster · 28 March 2006, 10:34

Further on this I was talking to the guy whose marina I am using at the moment, and he tells me he has never changed the impellers on either of his RIB engines (two 75hp Mariners, IIRC) since he got them new in 1995, never had any problems.

So perhaps they last better than I thought!

I suppose being rubber the age is as important as the hours run though - my engine only has 288 hours on it in 6 years but I think I will still change it over the winter so I know it is OK.

roycruse · 28 March 2006, 11:12

If the tell tale is gushing water - then your impeller is fine.

If its not gushing then you either have a blockage or your impellers worn.

I think impellors can get destroyed very quickly if you use your boat in shallow water and are constanly sucking debris into the water intake - grit and sand will wear it away in no time.

jyasaki · 28 March 2006, 19:12

Quote:

Originally Posted by BogMonster

Further on this I was talking to the guy whose marina I am using at the moment, and he tells me he has never changed the impellers on either of his RIB engines (two 75hp Mariners, IIRC) since he got them new in 1995, never had any problems.

So perhaps they last better than I thought!

The problem is not so much how long they last (which is, like any mechanical piece, variable), but rather what will happen when it fails.

Losing the impeller means no cooling to the motor. No cooling causes an overheat, which, if not shut down in time, causes oil to thin, and adjacent moving metal parts to come in contact with each other. This causes wear and breakage, not to mention stranding you on the water, usually at the worst of times.

So, you end up with a tow back to port ($500 to a couple of thousand), a motor repair bill (couple of thousand minimum, I'd expect), and a few weeks off the water. The $100 or so to replace the impeller is pretty cheap insurance, all things considered.

jky

BogMonster · 28 March 2006, 19:31

Couldn't agree more jky - that is why I am going to do it anyway.

I am a great believer in prevention being better than cure - especially when the safety of my neck may also enter the equation!