Old 25 horse - need for speed (at least a little more)

[chip65ss]

I recently took under my wing a 1969 14 foot aluminum sea king with an older 1950's 25 evinrude. The motor starts great and seems to run very well. Although I don't know much about outboards. Anyway what I would like to know is how fast should this boat be able to go. I had it out last night for the first time and it seems a little slow. There is a high speed ajustment knob and a low speed adjustment know on it and while I was on the lake I ran the high speed all the way up and it did help some. I also adjusted the throttle linkage a bit and got some more. It probable moves out at about 10 miles an hour, it's hard to tell without a speedo. Prop is in good shape. <br />Anyone with any experience with this I would appreciate you comments.<br />Thanks

 

[Paul Moir]

Re: Old 25 horse - need for speed (at least a little more)

Low speed jet adjustment:<br /><br />Loosen screw and remove knob. Start the engine and let it warm up. In forward, turn the shaft in (clockwise) until the engine sneezes, and then back off an 1/8th turn. Give the engine a few seconds to react every time you make the adjustment.<br /><br />At WOT (full speed ahead), turn in until it slows, then turn out until you reach highest RPMS. Re-do the low speed jet.<br /><br />If you get lost, the initial settings are:<br />High speed: 3/4 out from lightly seated (all the way in)<br />Low speed: 1-1/2 turns out from lightly seated.<br /><br /><br />Go here and follow the directions in Joe Reeves post.<br /><br />As for gross performance problems, you could be running on one cylinder. Try removing the top then bottom spark plug lead. If your idle doesn't drop when you pull a lead, that cylinder isn't firing. Another possibility is low compression. You do have a 50 year old engine there afterall. If compression is low, you may be able to bring it up by decarbonizing it. Search the forums for 'decarb'. <br />Get a manual. They can be ordered from here. (look at the top of the page) If you plan to keep the engine, it will pay it's own way. EDIT: If your engine truely is '50s, then it was produced before '55. Go here to figure out your precise year.

 

[alcan]

Re: Old 25 horse - need for speed (at least a little more)

Hi Chip<br />Ditto what Paul said. I am not familiar with your boat. But I would this that this combination (boat and motor) should be a little scarry at full throtle. This assumes a light load and your solo in the boat.

 

[chip65ss]

Re: Old 25 horse - need for speed (at least a little more)

Wow! I new I came to the right place.<br />I will give these ideas a try.<br />Thanks alot for the advise. I will post back after I test it again.<br /><br />Thanks again.<br /><br />PS This v-bottom sea king boat handles very well at low speeds, I will let you know how it handles if I get more out of it.

 

[Jwill]

Re: Old 25 horse - need for speed (at least a little more)

Your boat / old motor should do around 20 mph.<br />I had a 1980 25 horse on a 12' aluminum and it was perfectly safe. It probably done 25-30 mph.<br />I put the outboard on a 15' aluminum and it still goes almost as fast.

 

[NathanY]

Re: Old 25 horse - need for speed (at least a little more)

I just sold my 14ft Jon boat with a 1973 Evinrude 25hp on it. With me and all my gear in the boat, GPS at WOT was 27 mph. Very fast and very scary. I would look back and there would be no spray, except for off the motor.

 

[chip65ss]

Re: Old 25 horse - need for speed (at least a little more)

I did find out it was a 1955. Before I take this boat out again I would like to know if I should change the trim position? I think that's what it's called. (The angle of the prop associated to the boat.) I would think that this would make a difference too. Last time I had it out I had it set at the lowest angle possible(closest to the transom). Should I change this?

 

[G DANE]

Re: Old 25 horse - need for speed (at least a little more)

Hi Chip<br /><br />Trim position depends of boat. My brotherinlaw has a 14' runabout with a 73 25 Hp. Its in 3'rd trim hole, doing 28 Mph when he is alone in it. Smooth and strong running motor.<br /><br />Imagine you are on plane with boat, stern up. The antiventilation plate should be parallel with water surface.<br /><br />Are you sure motor is not mounted too low ? Antiventilation plate ( big plate above propeller ) should be even with keel on boat.

 

[chip65ss]

Re: Old 25 horse - need for speed (at least a little more)

The antiventilation plate is about 3 inches below the keel. I can't raise it more than an inch because the transom won't alow it unless I would try to change that. I don't think that would be a good idea. Has anyone else tried modifying there transom to make it higher. I think I read a post that discouraged it. If I did get this raised somehow would it really make that big of a difference.<br /><br />Thanks