59 Johnson 35hp - engine speeds up, boat slows down

[treefarmer]

Just bought a 1956 Crona Craft mahogany runabout with what was said to be a great Sea Horse motor. Runs ok, but when you increase throttle all of a sudden engine speeds up but the boat stops! Prop is tight and shear pin good. Is the slip clutch just letting loose at higher speed? Shifter works great, and it does move fine F and R at low speed. Help, it's driving me nuts.

 

[HighTrim]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Welcome to iboats.

Sounds like your prop hub is spun. You can have it rebuilt for less than the cost of a new prop if it is still in good condition. Test it by drawing a line across the hub and prop, or use the cotter pin as a center line. Run the prop until you hear it 'rev', then pull out of the water. If the lines are no longer lined up, she is spun.

 

[treefarmer]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Thanks High Trim. Sorry, but what exactly does 'spun' mean? Is the rubber part of the slip clutch no longer holding during normal use? Can just that piece be replaced? Sorry, I'm new to all this.

 

[CATransplant]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Yup, it's the rubber hub that slips. On outboards almost 50 years old, the original rubber in the prop is probably the same age. A prop shop can do the repair, but it's not a job for the home shop. You might also consider getting a new prop and keep the old one as a spare when you get it back.

It's always a good idea to have a spare prop on board.

 

[treefarmer]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Thanks CATransplant. I see you are in my area. Any recommendations for where to take for repair or buy a new prop? Sorry, I need all the help I can get. Thanks.

 

[F_R]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Anatomy of a propeller: There is a bronze hub in the center that is pinned to the prop shaft. There is the propeller itself, the blades part if you will. In between those two parts is a rubber shock hub. You can't see it but trust me, it is in there. The rubber is bonded to the bronze hub and is a very tight fit in the blades part. It is designed to slip when you get the prop tangled up in the trees, protecting the gears and stuff. The problem arises when the rubber's bonding with the bronze hub fails. Then the bronze hub spins in the rubber and you don't go. A prop shop simply removes the defective stuff and presses in a new bronze hub and rubber assembly. You can't do it yourself without a $10,000 machine. Machine cost guestimated.

 

[HighTrim]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

It's always a good idea to have a spare prop on board.

Cant emphasize that enough. More than once my spare prop saved my but when a tree stump snuck up on me!

Now,for my own boat, I buy the 2 piece props. The hub and blades are seperate entites. That way, if the hub goes, you need only replace the hub, or if you damage a fin, you need only replace the outer shell. Saves money, no need to rebuild, and you practically always have a brand new prop on for less than you would of spent rebuilding it.

 

[CATransplant]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

I have heard good things about Propulsion Prop & Marine in Hudson. Here's their website:

http://www.propfix.com/

For buying another prop, you can often find good or new ones on eBay for those pin-drive outboards. I bought one that was like new for under $20, including shipping. New ones run under $100, and you can order one right here on iBoats. Just click one of the prop links at the top of the Johnson/Evinrude Troubles page.

 

[CATransplant]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Cant emphasize that enough. More than once my spare prop saved my but when a tree stump snuck up on me!

Now, I buy the 2 piece props. The hub and blades are seperate entites. That way, if the hub goes, you need only replace the hub, or if you damage a fin, you need only replace the outer shell. Saves money, no need to rebuild, and you practically always have a brand new prop on for less than you would of spent rebuilding it.

Those are really nice, but I don't think they make one for an old pin-drive Johnnyrude 35.

 

[treefarmer]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

This is one awesome site! Thanks to all for your help. Maybe someday I'll know enough to help somebody else

 

[tonkagal68]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Just bought a 1956 Crona Craft mahogany runabout with what was said to be a great Sea Horse motor. Runs ok, but when you increase throttle all of a sudden engine speeds up but the boat stops! Prop is tight and shear pin good. Is the slip clutch just letting loose at higher speed? Shifter works great, and it does move fine F and R at low speed. Help, it's driving me nuts.

I am more interested in where you found the Crona Craft! My father owned and built the Crona Crafts. They were built by Tonka Bay Boat Works (now Marina) on Lake Minnetonka in the 1950s. I also have one that desperately needs restoration. Does it have the brass plate with the number on it? Fun to see this message.

 

[ezeke]

Re: 59 Johnson 35hp - engine speeds up, boat slows down

Michigan Wheel makes a good match prop for your motor #012028. http://www.iboats.com/012028-D-F-PJ...0661775--**********.749613039--view_id.689473