3blade prop for old 5.5hp Fisherman?

[Squeakit]

I am trying to get max top speed out of my old 1957 Fisherman (sounds crazy but it's become a challenge) So far, I have stripped 10lbs off the motor weight, built a small light 1gal tank for fuel, and now nothing remains but possible prop change. Motor presently has stock 2blade prop. I would like to try a 3blade and can anyone suggest where I could get one for this old engine?? Motor is on a lightweight 12ft jon boat and goes about 16.2mph GPS. Would like to try for 20mph. Am I dreaming and no, I'm not interested in running nitro in my motor, or doing anything that would ruin it. Any ideas, and please don't laugh too much. <G>

 

[steelespike]

Re: 3blade prop for old 5.5hp Fisherman?

A three blade prop is not usually considered a speed prop.<br /> You need to try to find a speed prop.It will be <br />hard to find but worth it if all you want is<br />speed.Your rig may be too heavy but if you arent too heavy it may work.<br /> Speed prop is 2 bladed and designed only for top speed.It may be difficult to get on plane but once there will push to maximum speed.<br /> The other thing to work on is motor height and trim.raise the motor a little at a time using<br />what we used to call rev sticks under the mounting bracket. Keep raising it till ventilation<br />becomes a problem.You could gain as much as 2 or 3<br />mph with as little as 1 inch in height.Then<br />trim in or out to the best setting.Generally<br />speaking once on plane move your weight back as far as possible.You want the boat to run with as little wetted surface as possible.<br /> I think the antique outboard site has races with<br />these little motors the may have ideas and info<br />at www.aomci.org.

 

[Squeakit]

Re: 3blade prop for old 5.5hp Fisherman?

Thanks for the info Spike - I don't know much about props and was surprised to learn that speed props are 2blade. Do you or anyone else know if the stock 2 blade prop can be modified for greater speed? I will definitely try raising the motor as suggested.

 

[dakotashooter2]

Re: 3blade prop for old 5.5hp Fisherman?

Steelspike confirmed what I have always heard. Supposedly two blade have less drag and possibly less slipage. The down side is that they experience/cause more vibration. Three and four blade props are reccomended for trolling motors because they reduce vibration at low speeds.

 

[Chinewalker]

Re: 3blade prop for old 5.5hp Fisherman?

Hi Squeakit,<br /> Unfortunately, being that the 5.5 OMC was never intended to be a high-speed motor, there really aren't any propellers out there to fit your need. There simply isn't enough power there to swing a more aggressive prop. Furthermore, the motor probably won't handle a lot of additional stress, as the aluminum rods have a habit of coming apart at higher revs. You might be able to do a bit of tweaking by using a later 6hp crank & rods to take advantage of the roller bearings. It would require some block modifications to accomodate the center main bearing. I'm not sure exactly what kind of mixing & matching could be done between the 6 and 5.5, but you could probably get some extra punch out of it that way.<br /> The ideal candidate for getting some extra oomph out of a small motor would have been a Mercury KF5, as they could take quite a bit more punishment. They ran them in Class J racing and a good one could creep over 25mph on a lightweight utility hull.<br />- Scott

 

[Squeakit]

Re: 3blade prop for old 5.5hp Fisherman?

I really appreciate the input, guys. I'm just a low-budget guy having fun with a few little motors and a little boat down here in Lake Havasu where most people run boats that cost a lot more than my house. I love to watch these half-million dollar monsters roar by on the lake and I fantasize about what I would do if I won the lottery - but that notwithstanding, I am enjoying the heck out of what I have. I am very new to this whole boating thing, but, I have always been a gadget guy and I love buying an old outboard for less than 100bux and clamping it on the back of my little jonboat to see if I can make it across the lake and back. Guess I'm a throwback to a time when boating wasn't a let's-see-how-much-money-you-got pastime. I know that most people are concerned about how they can get their 250hp motor to go 25mph faster, but there must be a few of us that are just interested in the challenge of making a small boat and motor do the best it can. I am very grateful for this website and all the information it contains. When we first moved down here, I didn't know an impeller from a propeller, but thanks to all the experts here I am learning about things I never knew before. I guess there was a time long ago when boating wasn't about displaying how rich you were, but more about having fun based on your own ingenuity. Sorry about the rant, but I ride a Kawasaki Vulcan because I don't choose to spend the money to ride a Harley just to be one of the in crowd (no offense to Harley riders intended). Thanks, guys, for a real good experience.