Johnson seahorse 4hp Half speed?

[pjsin]

Hi,

My johnson seahorse only seems to be reaching half speed. starts very easily sounds like choked up or firing on one cylinder. Both plugs have a good spark. However when I take one of the plugs out it is damp with petrol where the other is dry. On very rare ocassions it picks up and works as its suppose to. Then the next time I start it, it goes back to it's usual ways. It looks something is intermitant.

Any advice would be much appreciated.

Many thanks,

Andrew

 

[CATransplant]

Re: Johnson seahorse 4hp Half speed?

If you say both plugs have good spark, try a pair of new plugs in that little engine.

If that doesn't work, time to check compression.

On two-stroke engines, my first step is always to slap a new plug or two in. It's amazing how many times that fixes it.

 

[Scaaty]

Re: Johnson seahorse 4hp Half speed?

I would say to replace both coils...one might work giving spark out in the air, but not under compression. The tip is it picks up at times. Older original Johnson coils known to get cracked from heat and age...don't know how many motors I have picked up running on one cylinder. I have a 4hp too (84) good little motor..neighbor using it now (in fact I just gave another neighbor a 3hp to use on his dingy yesterday for an extended trip to the San Juans..both at one time needed a coil)

 

[pjsin]

Re: Johnson seahorse 4hp Half speed?

Super, Will give change the plugs, is changing the points a job I could do myself? Unsure of the procedure. Many thanks for your replys.

Andrew

 

[JB]

Re: Johnson seahorse 4hp Half speed?

We need the model number, Andrew. Over the years there have been several different ignition schemes on the little twins. Your description does sound like an ignition fault. Could be a failing coil, dirty points, failing condensor or simply an arcing plug wire.

Don't start changing parts. Throwing parts at an outboard in hopes of fixing an unknown fault too often results in added faults, and always results in unneeded expense.

Tell us the model number, do a compression check and let us know what you find.

 

[pjsin]

Re: Johnson seahorse 4hp Half speed?

Hi,

I have found the model number which is :

4BR79D

Many thanks for your continued advise.

Cheers,

Andrew

 

[F_R]

Re: Johnson seahorse 4hp Half speed?

That one has CD ignition. No Points. Checking it out requires a little bit more expertise, unless you want to start throwing parts at it till it works. You need a factory manual.

Exploded view of the parts at http://epc.brp.com/default.aspx?brands=ej&lang=E

 

[CATransplant]

Re: Johnson seahorse 4hp Half speed?

We need the model number, Andrew. Over the years there have been several different ignition schemes on the little twins. Your description does sound like an ignition fault. Could be a failing coil, dirty points, failing condensor or simply an arcing plug wire.

Don't start changing parts. Throwing parts at an outboard in hopes of fixing an unknown fault too often results in added faults, and always results in unneeded expense.

Tell us the model number, do a compression check and let us know what you find.

No disrespect intended, JB, but a pair of new sparkplugs is not throwing parts at an outboard. A guy oughta have a fresh pair on hand at all times. If it's missing on one cylinder, it's worth a try, and takes five minutes. If that's the problem, you're done.