Johnson V4 1978 85HP Seahorse Specs?

Hi everyone, I was compelled to join this forum since I just bought a 1977 VIP trihull and with a 1978 85HP Johnson motor (model 85ml78c) that is not running correctly, it has a tough time on cold start but runs just OK when hot but it is easy to start once it has been running. I was hoping someone might have some specs I need until I get a service manual for it. I suspect I am having ignition issues so I would like to remove the flywheel and inspect the points and stator and also replace the spark plugs. Does anyone know what the flywheel and spark plugs torque specs are? I believe the gap specs for the plugs should be .30 but have read it can be as much as .40 so I will probably go .35, any thoughts on this idea? The first thing I am going to check today is compression and make sure that is not an issue.

Re: Johnson V4 1978 85HP Seahorse Specs?

They're are no points to set. Flywheel nut torque is 105 foot pounds... anything less results in a sheared flywheel key and damaged C/S & flywheel tapers.

S/Plugs should be CHampion QL77JC4 plugs. The original recommended gap was .040. The revised gap made in the 1990's is .040. On some engines, one gap provides better performance over the other... try both.

Compression should be 100+ psi and even on all cylinders. What are your psi readings (all cyls).

Spark, with all s/plugs removed, should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

A common problem is fouled carburetor jets. In which case, clean and rebuild the carburetors.

Re: Johnson V4 1978 85HP Seahorse Specs?

Thanks Joe for your fast response, I am glad I asked, I would of torqued the flywheel to 50 to 60, had no idea it was that high. Took compression readings and they are not that great: the passenger top is 100, passenger bottom is 105 and the two drivers sides are both 110. What is the number one cylinder anyway? Anyone know the torque spec for the plugs?

Re: Johnson V4 1978 85HP Seahorse Specs?

Compression is okay... gauges vary. Spark,plug torque is 20 foot pounds BUT sometimes that seems like a little much. I usually just tighten them by feel. Standing in back of the engine, facing the spark plugs, the cylinders are numbered as follows.

2.....1

4.....3

Look closely and you'll notice that #1 is slightly higher than #2..... #2 slightly higher than #3, etc

Also, keep in mind... Drivers side (right) is "Starboard".... Passenger side (left) is "Port". Reasoning is definition of left or right changes depending on where one is standing/sitting..... Definiton of Port or Starboard does not change!

Re: Johnson V4 1978 85HP Seahorse Specs?

Thanks again Joe for your help. I am going to take your advice and get a carb kit.

hi I just bought the same engine do you still have your Johnson 85 hp did you get it fixed ?

1978 johnson 85hp said:

hi I just bought the same engine do you still have your Johnson 85 hp did you get it fixed ?

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The OP left 7 years ago. Why not start a thread of your own to get some answers?

Closed.