Johnson Seahorse 4 (cooling problem)

jmp

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Just aquired a johnson 4 o/b.It runs fine but no water was pumping.Dismantled the pump and turned the impeller round as fins set after standing for some time.When reassembled and tested, water comes fom the holes just under the steering swivel collar.None comes from the block as I expected.Can't see where it might emerge either.Engine ovviously getting hot so stopped!!

Anyone any info/ideas how to test the upper cooling areas.Tried to find details on web without success.Anyone know if manual can be downloaded etc

Engine No J4BRCRM
B032691

Thanks in anticipation!
 

VicS

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Thats an '84 model. You should have renewed the impeller!

The recurring problem I have with an '84 6hp is that corrosion squeezes the grommet at the top of the water tube over the end of the tube until it cuts off the water flow. The 4hp is similar but not identical. However since you get water from the exauhst relief holes that can't be the case although it could be restricted. You should put a hose on the bottom end of the water tube and make sure you get a good flow. The figure of 8 water channels in the head could well be blocked. Does the head show any signs of paint dis-colouration due to overheating.

Willsmarine are said to be good for mail order spares. (Google will find the URL)

The 4hp has no telltale (pee hole) on the cooling system (and no thermostat)

You might find the engine parts diagrams HERE useful
 

jmp

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Thanks Vic,

Your advice and responses have in the past and now been very helpful to me and no doubt others.
Can't beleive I never thought of testing the water tube upwards !
The engine I doubt has done more than a handful of hours and is pristine,almost as new .I guess the impeller is original, and will of course be replaced once to hand.
There is no heat discolouration and I stopped well before damage.
Will do as you suggest andsee how it pans out!
By the way could not trace year etc myself.It seems the search areas on the sites I have are not too friendly,and even putting the precise model no in the response is blank!
 

andy_wilson

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In response to sailorman, these were one of the best engines OMC produced. Incredibly light for a twin, and smooth running because of it. Plenty of torque and ideal as an aux. for a bigger boat. Std. Long an XL shaft available and easy to switch between std. and remote tank.

Excellent corrosion resistance and well over cooled so seldom giving problems as you describe.

Mine is the 1989 derivative and in 18 years has had 2 sets of plugs and the odd rinse and squirt of Duck Oil ,and still runs perfectly despite suffering siezure due to a very minor head gasget leak that let salt water in to the upper cylinder.

Easily fixed by removal of head, soaking upper piston in oil to free, clean all up and reassemble with Hermatite - sod the new gasket!

As you can see, I'm a fan.

They have no tell-tale. Water splutters from the exhaust relief at the back of the leg between the powerhead and waterline. I suggest you run it up under load and see if the cylinder head and exhaust manifold get too hot to touch. I suspect you will find absolutely no problem and it will give you many years of service.

Mine has more recently been pressed in to dinghy use and pushes me, my daughter and the Suzumar up onto the plane and will run like that all day at 2/3 throttle - or at least until the 12 lit remote tank will last.

This link will get you a free PDF of an exploded engine / parts list. I think there is a link to manuals as well.

http://www.evinrude.com/en-US/Accessories/Literature/
 
G

Guest

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[ QUOTE ]
Just aquired a johnson 4 o/b.It runs fine but no water was pumping.Dismantled the pump and turned the impeller round as fins set after standing for some time.When reassembled and tested, water comes fom the holes just under the steering swivel collar.None comes from the block as I expected.Can't see where it might emerge either.Engine ovviously getting hot so stopped!!

Anyone any info/ideas how to test the upper cooling areas.Tried to find details on web without success.Anyone know if manual can be downloaded etc

Engine No J4BRCRM
B032691

Thanks in anticipation!

[/ QUOTE ]

Johnson in their W/shop manual specifically warn against turning impellor around ... saying it will destroy itself.

I had mine block up and injected neat concentrated spirit vinegar in the engine block exit ... let it stand on side ... then stood up to let it drain out bottom ...

The engine was then stripped for other reason and the guy had to replace leg to block gasket .... but found that water pump casing had cracked next to one fixing point ... and he reckoned it was common.

Engine is fine now ...
 
G

Guest

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No Tell tale ... I thought after reading the w/shop manual that tell tales was same as the 4.5 twin I have ... a small hole that is on a curved section tucked away right underneath. It's a daft hole as it is not round but oval and only about 2mm diam. It is also near impossible to poke a bit of wire in to unblock properly.

Interesting ....

As to year of manufacture - that is given by a code set of letters and the number ... shown on their web-site but as a sub drawing within a main one ... if I can get the url or a scan of the page in manual I'll pass on ...
 
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