5.5Hp 1961 SeaHorse -Water Pump Not Working

[Loper4]

I have a 1961 5.5HP Johnson Seahorse which, which upon the first start of the season this year immediately got very hot and was near steaming. It only ran for a minute or so before I turned it off. Upon teardown, I have gotten to the water pump and have found that the impeller is in good condition. This is my first attempt to fix an outboard motor and have found that that the tear down was more complicated then I was thinking. Does anyone have an idea on how best to proceed on checking the coolant system well I have the lower end disassembled?

 

[OptsyEagle]

Re: 5.5Hp 1961 SeaHorse -Water Pump Not Working

I would probably do the following first. Try to connect the garden hose to the copper tube that goes up into the motor. You may be able to seal it enough with just your fingers and if water is coming out of your exhaust ports then you know that the cavities are not completely clogged. I would also fire some water down the pump holes to see if it flows out the intake screen, etc. to verify that no obstruction got in there. Now if you inspected the motor's pee spray before you turned it off, when it was overheating and it was spraying water, then the above test is most likely redundant.

I would then inspect the thermostat. It is located in the little triangular section right above the powerhead. It has three screws to remove. In your case the thermostat would be either clogged up or it has failed closed. To verify a failure you could put it into some water in a pot on your stove. Heat it up to around at least 145F and ensure that it opens. If not that is your problem and replace it.

If the two above tests are positive then I would focus on whether your impeller has the pin properly in place to turn it or if it has disconnected from the brass center. Now personally, I wouldn't really care if the impeller did disconnect from the brass center (except it would be very good to know) since if my motor overheated and I went to the trouble of lowering the lower unit, my motor would get a new $12 impeller, whether it looked like it needed it or not. Now, if all things are a go here, I would suspect that the copper tube must have come out of the rubber grommet (inspect that grommet very carefully as well on the pump housing). When reassembling a lower unit on a 1961 5.5Hp you need to manually place the copper tube into the pump grommet. It will not automatically align by itself. I also shine a flashlight back down the shaft from the top to ensure it is in. If not the powerhead gets no water.

When you eventually identify your overheating problem, I would probably want to test the compression of the motor now to see if the overheating caused the cylinder head to warp or damaged the head gasket. Compression should be around 85psi plus or minus 10, and more importantly it should not vary by more than 10 psi between the two cylinders. If your compression is off, let us know and we can probably help you fix that as well.

One last thing. Before my motor would be reassembled, I would get a new exhaust gasket OMC #313065 or Sierra 18-2901 (about $5) and a new crankcase seal OMC#303355 or Sierra 18-2892 (not sure the price but not expensive and extremely critical to protect the motor) Good luck.

 

[Loper4]

Re: 5.5Hp 1961 SeaHorse -Water Pump Not Working

Thanks a million. I will check the t-sat first.

The one thing that happen while dissassembly of the pump housing is that the copper coolant pipe and shaft leading up in the engine came disconnected at the top end. I have tried to remount it but am having trouble.

Also there is a what I would call a hold down rod that extends all the way down from the motor to the gear sub assembly near the impeller and wraps around the grear shaft mounted to the propeller. I am not sure how to remove this as I believe that I need to in order to reposition the water pump shaft and coolant pipe. Do you have any ideas on how to (if needed) remove the hold down rod.

I feel like I just jumped off a cliff......

 

[OptsyEagle]

Re: 5.5Hp 1961 SeaHorse -Water Pump Not Working

The copper coolant pipe should stay up in the upper part of the motor when you lower the lower unit, so I suspect that if it came loose, that may be your problem. Unfortuneately I have never replaced a copper tube so I cannot advise on how to reassemble it. Perhaps someone else can provide advice there.

I am not sure what you mean when you say a "hold down rod". The only other rod that comes down with the lower unit, that I remember is the shift rod. This is the rod that you disconnect up above (about two hex nuts) to lower the lower unit. I never had to remove it to change an impeller and trust me, you do not want to. If you are speaking of another rod, let me know.

I should also add in my advice above about firing water up the copper tube to see if it comes out the exhaust. That test will not work on this motor because your powerhead is off the unit as we speak. You will be able to see if the copper tube is clogged though. I would just dribble a little water down the copper tube to check this out. You will not need a garden hose for that. Right now, however, I would focus on why your copper tube has come off the upper unit. This never happened with my motor.