Prop suggestions on a 140 looper

[1990 looper]

Hi, My 140 is running great and have only run test in a barrel. Hopefully this weekend I can get on the lake and do some WOT and etc. The engine currently has a slightly dinged alum prop. There seems to be a large selection of used SS props out this for these motors. I recently found a 14,25 x 23 SS omc prop for less then a $100. My boat is a 19' Ranger fisherman which is fiber glass and has a deep bow. So, it is heavy and sits low in the water. Current prop cavitates a bit..
So, basically I looking for a rough idea where to start?

 

[flyingscott]

What size prop is on it now.
What rpm are you turning
Does your prop cavitate because you have it trimmed to high.
Questions that need to be answered.
Rule of thumb is light load prop for maximum rpm. Light load= 1/2 tank of gas and you
If you prop it for the bottom of the rpm range you will generally be the fastest with the slowest holeshot and it will struggle with a load.
If your boat is heavy may want to look at a 4 blade

 

[sutor623]

Wellllll, first off what year motor is that? I think the 140 loopers were all rated at the crank, not the prop, so really a 115 at the prop. (May be wrong on that). Smaller the load, bigger the prop. 23P sounds big, but if that is a Ranger bass boat, it may really come out of the water, decreasing drag.

I have a very heavy sea-worthy boat, 20'er, that sits low in the water, and my Evinrude 130horse spins merely a 17P prop. This brings me to 5500RPMS at WOT, with 38MPH with a relatively heavy load. Perfectly set up if you ask me.

You need to find out where you RPMS are, and try and get that prop to bring you from 5500-6000rpms on a light load. Maybe check out the ranger boats section and see what they are running, but I am guessing that a 19-21 pitch would be more in line.

 

[racerone]

A 19" pitch might be a better prop to start testing with.

 

[metriccrescentwrench]

I think the 140 loopers were all rated at the crank, not the prop, so really a 115 at the prop. (May be wrong on that). .......

Nope, all manufacturers went to rating their engines at the prop in the early '80s.

Just as a point of comparison, I have an 18 1/2 ft. bass boat with a 140 HP Crossflow and a 19" pitch Renegade prop (4 blade stainless) which is a good match... good hole-shot and WOT rpm of around 5500. IMO that 23 pitch prop won't work for you.

 

[jakedaawg]

I am not gonna coment on the pitch (although a 19 would be a good starting point, haha).

What I will say is you all need to really think about going stainless. They cost more. With all your fishing and tubing and skiing stuff in the boat you will not notice any substantial difference. Really. It would take a finely tuned racers ass to recognize the difference in hole shot and top end with all the crap people load in their boats.

Also, if you hit something now we are not talking about a $85 dollar weld and balance we are talking $170+ to repair the prop, not to mention the clutch dog, vertical shaft.....

I would bet just about anybody that they cant tell the difference between 41 and 43 mph without looking at a speedo or GPS or whatever...

end rant.

 

[sutor623]

Yea I agree. I have slapped up a $100 aluminum solas prop a time or two on my rigs with no damage to the prop shaft, and was thankful as I happily bought another $100 prop to replace them each time.

Now, these performance bass boats that have been engineered to run certain engines, and have had plenty of test runs by the dealers to find the "perfect" prop, that's another story. My friend has a 21' Ranger with a Merc 225 set up perfectly, and that thing FLIES!!!!!!!!!!!! But if its just us users that have to buy a prop and then either rejoice or cry, its a bit more difficult to justify going with a new stainless prop. (Not that you are looking for new)