4hp trouble and questions

[jaymasta]

I bought a 1975 4hp johson motor It seems to run much nicer in a bucket at home then it does out on the water though. When I use it on my boat in the ocean it doesn't seem to rev up nearly as much as it should and coughs quite a bit and seems to surge up and down at random and it also stalls out if I idle it to low (not nearly as low as I can idle it in a bucket at home). Iam wondering if It may have something to do with the "low speed", or "high speed" mixture adjustments on the front of the engine, and wondering how they should be setup ?
The engine has good flow out of the eight little holes on the leg of the engine(telltale) however the waterjacket on the side of the engine does get hot to the touch quite quickly. I ran it for about 15minutes and it was very hot to the touch but not hot enough that water would steam off of it if I sprayed it with water. Iam wondering since I have good flow out of the telltale if something is broken or leaking somewhere and making it to the telltale but not making it through the engine? Does water have to flow through the engine to make it to the telltale exhaust ports?
I will rebuild the carb etc in a few months but it is prime fishing season right now and don't have the time or money to do it right now. I would really like this engine to run reliably as it does in the bucket at home on the ocean.
Any tips or advise would be helpfull, my friend says the surging and stalling probobly has to do with the 2 mixture screw on the front of the engine, so I would like to know how to check and or set these up properly, and to know if my cooling system is working properly, I assume if it isn't and the waterflow is bypassing the engine it could be overheating and this could cause surging problems as well, how would I know if its overheating?
Thanks in advance

 

[Vic.S]

Re: 4hp trouble and questions

First check/clean/set or replace the plugs and check you have good sparks .

J6C gapped at 0.030"

The instructions for setting the carb needles are on the Engine FAQs board
http://forums.iboats.com/showthread.php?t=167352
but if it requires much adjustment from the basic settings then suspect that the carb needs cleaning.

The water jacket you mention. If you mean the flat plate held by 8 screws then that is the exhaust manifold cover and on these small models is not water cooled. It may well get quite hot.

Good water flow out and not steaming suggests the cooling is OK

Also on the Engine FAQs board find and read "Awakening a sleeping outboard" as its new to you a fair bit there is relevant.
(checked the gearcase oil?)

 

[Rick.]

Re: 4hp trouble and questions

Great little motors. One thing I would add is the importance of adjusting the needles on the water, not in a bucket. Your reference to coughing could well be a too lean slow speed needle. In regard to surging I think Vic is pointing to spark concerns and I agree with everything he has said. The 4 HP has no thermostat. Best of luck. Rick.

 

[crxess]

Re: 4hp trouble and questions

Agreed, work on the adjustments and make sure the carb is clean. Fuel restriction can cause surge, over heating, low rpm's.

Also, hull design/boat weight/prop size greatly effects performance. A heavy or non-planing hull will need a lower pitch prop to reach correct WOT rpm's.

 

[jaymasta]

Re: 4hp trouble and questions

First check/clean/set or replace the plugs and check you have good sparks .

J6C gapped at 0.030"

The instructions for setting the carb needles are on the Engine FAQs board
http://forums.iboats.com/showthread.php?t=167352
but if it requires much adjustment from the basic settings then suspect that the carb needs cleaning.

The water jacket you mention. If you mean the flat plate held by 8 screws then that is the exhaust manifold cover and on these small models is not water cooled. It may well get quite hot.

Good water flow out and not steaming suggests the cooling is OK

Also on the Engine FAQs board find and read "Awakening a sleeping outboard" as its new to you a fair bit there is relevant.
(checked the gearcase oil?)

That helps me a lot, I though it was a water jacket but good to know that it is the exhaust manifold. I will go ahead and replace the spark plugs, and check for good spark as well, and adjust the carbs according to the FAQ and see if it will get me through the next 6-8 weeks or so. I will rebuild the carb in the off season but for now the fishing is extremely hot which has been a rarity here the last 10 years so I would like to do as much as I can over the next 6-8 weeks or so, thanks again for your help, any other tips are appreciated.