120hp Johnson

Hey

1. New to boating
2. Got this sweet boat and was all going pretty sweet for the last 8 months
3. now all of a sudden the refs only go to ike 4000 (if that lucky) and cruising around at the odd 15- 20 knots aint how it is suppose to go..... Where do I start looking to get this fixed up...

Any help appreciated

Re: 120hp Johnson

Do the basics first. Compression and spark test. Spark should jump a 7/16 " open air gap on a spark tester. If they pass look into the fuel system.

Re: 120hp Johnson

Yep... what Boobie said. And get back to us with the compression reading of the individual cylinders, and also what kind of spark did you encounter.

Re: 120hp Johnson

Thanks Guys

Did the compression test (not very good I think)
1. 60 PSI
2. 50 PSI
3. 60 PSI
4. 50 PSI

Manual says it should not be less than 100 PSI.....

Re: 120hp Johnson

Compression will vary with the speed of which the engine is being cranked over with the electric starter. The engine should be turning over at approximately 300 rpms or faster.

If the engine is actually turning over at a normal fast rpm, then yes, I would assume you have a problem.... BUT.... if it is cranking over rather slow, check for a low or faulty battery, loose battery cable(s), tight but dirty battery cable connections, etc. Remove all cables related to the electric starting system including the starter solenoid and engine ground, clean the terminals and whatever they connect to, then tighten them securely with a wrench or pliers.

Cylinders 1 & 3 are the starboard bank and have even compression of 60 psi, and cylinders 2 & 4 are the port bank with a even compression of 50 psi. This leads me to think that you have a slow cranking engine and if so, this would not be fast enough to have the stator generate enough power to energize the powerpack.

Let us know about the cranking speed of the engine.