Can I upgrade old school prop to newer?

[tater76]

Hey folks, first off, thanks for all the help you all and the site have given me in the last few weeks. I have a new dilemma though, through the advice on another thread I was able to get my 1973 55hp chrysler to provide enough power to get my 1976 crestliner tri-hull to plane out. (Finally woohoo!) However, I have come to understand that I may be underpropped? I am running what came on the motor when I bought it. The stamping reads 10X10, it has 14 splines, and some backyard mechanic tried his hand at cleaning up the edges. (It looks pretty rough, lots of grinder marks). I have done my homework on pitch and all of that, my question is can I run the newer style prop on this older motor? I'm talking about the more aggressive, flared, almost thru exhaust looking props. I want to buy one from iboats but will it be this newer style? The pics on the site show as such when I go to check out, but?.... I just don't want the same thing I have with the same results. Oh, and the motor makes 5500rpm at WOT, but runs best at 5000. Any suggestions would be great, even if it doesn't mean going with the new style prop.

Thanks

 

[Frank Acampora]

Re: Can I upgrade old school prop to newer?

Assuming it is the single carb 55, Simply put: No! There is no new style prop that will fit that engine. However, if you ask Franz at franzmarine@aol.com nicely, he MAY have a nice old-school bronze performance prop for you.

I have a couple of Michigan bronze 3 blades, a Columbian bronze 3 blade, a few aluminum 3 blades and the on on the avatar is a Michigan 2 blade AJC bronze. In reality, none is better than the other except for the 2 blade racer which is the correct prop for a 10 foot boat.

Of course, you can do anything you want if you are willing to throw enough money at it.

 

[tater76]

Re: Can I upgrade old school prop to newer?

It is a single carb 55hp, Dang! I thought I could gain something by getting the new style prop. So do you think it would be ok with an 11 or 12 pitch? I primarily use the boat for cruising, fishing, but I want to pull a tube for the kid. If the speedo works correctly(doubt it) I can only pull 20mph. However, the boat is getting on plane. Any thoughts?

 

[Frank Acampora]

Re: Can I upgrade old school prop to newer?

With a 10 inch pitch, 20 sounds about right. My 15 foot Glastron runabout was originally powered by a 1967 Chrysler 55 and I used a 10 X 13 bronze Columbian prop on it. With just the driver, that boat went 27 MPH. So, depending upon the size and weight of your hull, you may be able to step up a pitch or two. What bothers me though is that with that 10 pitch prop you are still only getting 5500. Is your hull 16 or 17 feet long? I was swinging 5500 on the Glastron with the 13 pitch. Check to be certain compression is high, the timing is correct, and the fuel system is delivering all it should. Be certain the points are clean and gapped correctly.