Home › Forum › Ask A Member › 1956 Johnson 30 hp won’t accelerate boat up on plane! › Reply To: 1956 Johnson 30 hp won’t accelerate boat up on plane!
If the throttle valve is opening all the way, my money is that you’re only running on one cylinder. It is surprising how deceptively well some engines….like yours…will run, on just one cylinder, if you don’t have an experienced ear for it. You need to do a compression and spark test, as basic first steps. I believe you should have at least 100 pounds compression (Bigtwin/RD fans, correct me if I am wrong on that) and the spark should be nice and blue, being able to jump at least a 1/4″ in open air. If the ignition hasn’t been serviced in awhile, that should probably be done, regardless. The term “completely restored” is probably one of the most vague, misinterpreted terms in all of mechanics. It all depends on who did what, and when.
Long live American manufacturing!