?'s on '71 50 horse

[blackhawkdc]

I have two questions on my Johnson 50 horse. Its the 1971 Hydro-Electric 50 horse twin. <br /><br />My first question is straight forward. I've been recommend to "Link and sync" the motor. What does this involve? I'm an automotive mechanic, but not much experience with boat motors. <br /><br />My second question is this. What prop would be recommended for this motor when installed on a 1971 Crestliner 14 foot aluminum runabout? It currently has a 13 3/4 x 15 prop on it I believe. It seems a bit big for the motor compared to the prop on my father's 45 horse Merc pushing a 16 foot Sylvan fishing boat. <br /><br />The problem I am having is that the motor has no power. It won't build RPM's at all and won't even get the boat up on plane. It sounds the motor is only topping out at about 1500 RPM's max. I already rebuilt the carbs, replaced the rectifier and one ignition coil. Fresh plugs and fresh gas. Any other ideas?<br /><br />Thanks in advance,<br /><br />Seth from Minnesota

 

[CATransplant]

Re: ?'s on '71 50 horse

That 15" pitch prop should work just fine on your little boat. In fact, that boat should fly with your 50.<br /><br />Sounds to me like the engine's still running on one cylinder. Time to check the ignition again and fix whatever's not working properly.<br /><br />For the link and sync operation, get a manual. It's not all that difficult, but the photos and instructions will help a lot. <br /><br />I haven't worked on that model, so I don't have any specific tips for the operation.

 

[Goodoleboy]

Re: ?'s on '71 50 horse

Howdy Seth!<br /><br />A link&Sync. procdure is the process of seting the carb. butter flys to start opening at the exact same time as timeing begins to advance. They both have to happen at precisley the same time.<br /><br />That could very well be the problem you have. Your problem could also include an air leak some place in the fuel lines.<br /><br />The prop sise has little to do with how well your motor runs. <br /><br />Even if is slightly over proped it should still turn up to about 5000 or so.<br /><br />After the motor is running strong. And the engine cant turn about 5500, then I would mabey try droping down on prop sise.<br /><br />Make sure motor is not setting to deep in water. Anti cav. plate should be even to a little above keel of boat.<br /><br />I would srongly encourage you to buy a OEM service manual for your motor. Makes boating life much easyer.<br /><br />Good luck!

 

[R.Johnson]

Re: ?'s on '71 50 horse

The very first thing on that engine is a compression test.

 

[blackhawkdc]

Re: ?'s on '71 50 horse

Thanks for your tips. I'll look into the service manual for the link and snyc adjustments. I was kinda wondering on that and now that may appear to be my problem. AS it appears that it pulls all the timing advance in before giving the engine throttle. So I'll check that out next chance I get. <br /><br />R.Johnson, I have checked compression and achieved 150psi on both cylindars.<br /><br />Thanks again,<br /><br />Seth from Minnesota