Johnson v4 sea horse 1979

[The big gibbo]

Hi, I've just got back from a weekend away with my boat. Once I got her in the water and fired her up I felt as if it wasn't going at its top speed. Well I'm certain it wasn't! I checked all the sparks and 3 out of the 4 were warm and the 4th one was still soaked in fuel! Is this not firing? I change the sparks around and the same happens to the same cylinder. Could it be a ht lead fault?

 

[Scurvy Knave]

Re: Johnson v4 sea horse 1979

sounds like that cylinder is not firing. A quick test is to run it and pull the plug wire on the suspect cylinder. If the RPMs don't change, that cylinder is not firing.

A quick test would be to check if the plug is sparking. If sparks is good (with a spark tester), check compression. Go from there.

 

[The big gibbo]

Re: Johnson v4 sea horse 1979

sounds like that cylinder is not firing. A quick test is to run it and pull the plug wire on the suspect cylinder. If the RPMs don't change, that cylinder is not firing.

A quick test would be to check if the plug is sparking. If sparks is good (with a spark tester), check compression. Go from there.

How would I check the compression on just that cylinder?

Thanks for the reply!

 

[fishmonster13]

Re: Johnson v4 sea horse 1979

How would I check the compression on just that cylinder?

Thanks for the reply!

you would want to check the compression on all cylinders and they should be with in 10 - 15% of each other
but you will want to check that you are getting spark on that cylinder first

 

[emdsapmgr]

Re: Johnson v4 sea horse 1979

That engine has two identical power packs, one for each head. Try swapping them and see if the "no spark" problem moves to the other head.

 

[The big gibbo]

Re: Johnson v4 sea horse 1979

I moved the power pack over and still no spark, I changed the coils over and still no spark so took apart the ht leads and found that the was a loose connection! And hey presto it works!!!

 

[Scurvy Knave]

Re: Johnson v4 sea horse 1979

Glad to hear it. Everyone loves a happy ending.

happy boating