Need Help selecting a prop for Cobra Outdrive

"First let me say hello to all

"First let me say hello to all here i have been working on this boat for two years She is a 245 1989 Trophy Hardtop.i just
installed a 351 Windsor Engine from Jasper and rebilt cobra outdrive with new water manifolds and risers on her
AND im very excited about putting her in the water soon.MY question is this the prop to use
i will be making some fairly long runs so gas mileage is of great importance.the boat will be on the Chesapeak Bay around the Pocossin VA area
I have read a great deal of articles on props and sadly im very confused on this issue.there is currently an aluminum prop on the boat.the previous owner said it suked anyone here familiar with this boat
type and a good prop pitch for the C BAY.also will do some fishing in the ocean a few miles out
but not to far Thanks for reading
this post"

"Mike,

First of all let me

"Mike,

First of all let me say welcome aboard and I can appreciate your confusion regarding props, you're not the first person to be confused.

Let me clear a few things up. #1, prop size is determined by engine RPMs, not boat brand or boating region. Your engine was designed to operate within a sepcified maximim RPM range. For warranty reasons, I would find out from Jasper what that range is. You can choose to favor one end of the curve or the other but if your engine does not achieve max RPMs within the recomended range you are risking damaging your engine. You will either overrev the engine or lug the engine. Both can cause premature wear of internal engine parts.

#2, prop selection is trial and error. You start with what you have. If it's in decent shape, try it. See where your RPMs are. Keep in mind, you're looking for WOT max RPMs. Also keep in mind, that's a fresh engine so don't thrash on it too hard until you have some hours on it. Also, see what you have available to try. If you have and buddy with a similar package, see what he has and experiment. Merc. Alpha props will also fit your drive although you may need to play with the spacers to get it locked on.

Based on the information you provided, I would start with something in the 17" pitch range. That's a heavy boat with that hardtop, so you might end up dropping down to 15". Since you're looking for economy and doing mainly fishing, I would keep in the lower side of the RPM range this should be the most economical. Also, if you can cruise without cracking the 4bbl (if you have one) you'll spend less time (and money) at the fuel dock.

Good luck and have a great season.

Rick

P.S. I was working down on the Chesapeake today and it was snowing."

"Thanks Rick,
sorry it took a

"Thanks Rick,
sorry it took awhile for me to thank you i have been out of town.the boat will do about 30 Knots
with the prop that is on her i cant see the #s on the prop though to tell what im turning. but i believe thats pretty good for that boat dont you.im thinking the previous owner wanted an
SS Prop real bad.because that speed is pretty good for a single prop on a 245 Hard Top
also put kodiac cadium brakes on the trailer this past week end bought those from Chesapeake Trailer,on Military highway the ladies were very helpful in me spending my money
thanks again"

Ladies usually are...


Bes

Ladies usually are...


Best of luck