What pitch will give me best overall preformance

[888MFG]

I have 20 foot fiberglass 1984 Sport Craft center console 200 Fisherman with a Johnson V4 140 2 stroke outboard. The engine is mounted on a Stainless Marine 24 Inch Bracket. Currently I have 13-7/8 x 17 aluminum 3 blade propeller. It is very slow to get up on plane but reaches top speed of about 25 mph at 5000 rpm. Any recommendations?

 

[harringtondav]

The rule of thumb is 200 rpm WOT change for each 1" of prop pitch change. A lower pitch will get you on plane faster, but will raise your WOT rpm, and sometimes your top speed. You want a prop that lets your motor reach, but not exceed the motor's max rated rpm.

Without more info, it looks like you could pitch down. 16" or 15" pitch.

 

[dingbat]

You have something other than prop problems.

Your 400-500 rpm low and your current prop isn’t far off base. Should be an easy 30 mph boat

When was the last time you did a compression check?

What make and model prop are you currently running? How old? What condition?

Tell us more about your bracket setup

 

[888MFG]

These pictures are from the day I bought the boat. Nothing has been modified but I did clean it up. It had been in water and i had a heck of job cleanin g up the stuff growing on it.

 

[dingbat]

I was going to comment ans say that I've never seen a bracket on a CC until I noticed the hole in the transom covered over.

At this point all bets are off. I would check compression to make sure the motor is running properly. Being modified, lots of variable to consider. Motor weight, weight distribution, etc.

 

[jimmbo]

How clean and Smooth is the hull right now? Even a slightly dirty and rough surface will slow down acceleration and reduce Top Speed

 

[888MFG]

the hull is as clean a new borns ass.

 

[WesNewell]

With a 24" setback, the engine appears to be mounted way too low causing a lot of drag. Hard to say without seeing the engine at a position inline with the hull but I'd say you probably need to mount it about as high as it will go on the setback plate and that may not be high enough to get max performance. Once you have the engine mounted for max performance, you will likely see a jump in engine rpm from the reduced drag. Outfitted properly , you should see 40 mph if the dry weight of the boat is 2000#.

 

[Scott Danforth]

being a converted hull with a long shaft motor, my guess is the AV plate is about 5" below the surface of the water and it plows

I have yet to meet someone who is happy with a converted hull.