I'm going to be traveling in a week or so to see a Johnson 75 HP Stinger. The owner is quite a motor head and has done just about anything mechanically that can be done (new reed valves, bearings, seals, gaskets, coil, wires, paint, anti-seize on all of the head bolts.) He bought the engine from a friend who bought it from a relative, put in a his shed ten years ago, but never touched it after that. Current owner bought it to mount on an Allison (sp?) racing boat he is restoring but has decided to go with something bigger and can use the money. The engine has never seen saltwater. Owner says it runs smoothly with a throaty growl when juiced.
If I buy it, I will be mounting it to a 1960 Glasspar G3 centerdeck. I've seen several pics of these engines on G3's and they look like a perfect fit. The engine owner had a G3 himself with a 65 hp Merc and thinks the Stinger is a great match.
My question is if there are any known problems with this engine I should watch for before making a purchase. I will appreciate any input from those in the know. Thanks.
You definitely want to hear it run, preferably on a boat but at least idling in gear in a barrel. When these Johnrude Triples are starting to wear out internally, they won't idle well.
So if the motor sounds good with no nasty Thrashing or Gnashing, idles well in gear (with load on it), and is in the condition described, it's likely a good one.
You could take a compression check after it's been run. I'd be concerned if there's more than a 5psi variance between cylinders. Ideally all 3 should be the same. Barring a leakdown test, that's about the best you can do.
A thorough test on a boat, in the lake, would be ideal but at least running it in a barrel will give you some exhaust back pressure and prop loading, which is better than nothing.
If the motor can't be run for whatever reason, I certainly wouldn't give a premium price, no matter how clean it looks.
My thoughts also. I don't have a lot of faith in the 3 cylinders. I've seen enough of them self destruct. If you're going to buy it I would run a higher octane in it also. I like all 3 major brand outboard companies, but in that HP range I like the Merc in line 4 cyls better. They seem to be much more dependable to me.