Steamy outboard

[elsie1]

I have a 20 Hp johnson outboard (model no 25e 75b). It runs fine but after about two minutes cooling water stops flowing at the exit point halfway up the midsection and exhaust no longer exits from the position just above the prop. after another minute it overheats.

Has anyone got any Ideas ???

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[GrahamSC]

HI
Sounds like your engine needs flushing with a descaler, there are plenty posts on this forum on the best way to do it. Is the lintake clear, saw one recently where the leg had been antifouled, blocking the holes
Regards
GahamSC

<hr width=100% size=1>Never recovered from loss of Tot, 1974

 

[VicS]

I have had almost exactly the same problem with a 6hp Evinrude.

The trouble was caused because the pipe from the water pump terminated IN what I can only describe as a rubber grommet which was itself located in a aluminium casting. Corrosion of the aluminium eventually squeezed the rubber over the top of the pipe restricting the water flow and eventually stopping it all together. It would not have been a problem had the pipe passed completely through the grommet but that was not the way it was designed.

The first time it happened I discovered that a wire pushed up the pipe after removing the lower unit came up agaist something squidgy, the rubber. I sorted it out then by just cleaning it all up and putting it back together again but realised that sooner or later it would happen again.

The second time I obviously went straight to the problem but this time the grommet was not really reusable as I felt it was important that the copper pipe could not come into contact with the aluminium.

I decided that a modification was called for so I fitted an O ring of such a size that a seal would be made between the pipe and the tapered hole in the aluminium bit, above that I had fitted a nylon sleeve which keeps the pipe centrallised and presses the O ring down in the bottom of the hole and then above the flared top of the pipe I fitted a nylon spacer washer so that when put back together the whole lot is gently compressed. Very difficult to describe without a diagram and only feasible if you have the materials handy and access to a small lathe ( I also made my own O ring as I have an O ring making kit.)

It is a fairly major job as both engine an gear box have to be separated from the leg and it makes sense to change the water pump impellor and gear box seals at the same time. In my case the engine is a long shaft model and the water pump can be damaged if the extension piece is left on the leg and not removed with the gear box. (Learnt by experience).

You dont say how old the engine is but bearing in mind the demise of OMC you may find spares are no longer available.

Incidentally I can seen no signs of corrosion in the water passages so far as I have been able to see them without dismantling the engine itself and water from a hose passes freely both ways from the telltale connection after removing the thermostat.





<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[elsie1]

Thankyou for your valuable advice, I'll do the flush job first, if that fails I'll go for the squashed pipe theory. Cheers, have a good weekend.


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[William_H]

Like VicS my experience is with 6HP long shaft. It is relatively easy to remove gearbox pump from the shaft. Connect a rubber hose to the copper pipe going up to the engine and connect to you garden tap. You should get a good flow into the engine out the tell tale and mostly out of the engine into the leg muffler area. If you get plenty of flow then the problem is in the pump if no flow the problem is in the engine. I have had a recurring blockage in the copper pipe which responds to a bit of rigging wire pushed up it. It seems to block at a bend half way up. May be my problem is closer to what VicS described. it is however a big job to remove engine from the leg. I recently fitted a new pump kit impeller and housing and this improved the cooling enormously. Incidently parts seem to be available (at least in West Australia) as Bombardier now own Johnson Evinrude. We won,t talk about price however regards ole will

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