74 Starcraft with Johnson 115

[eckhoffb]

Hey guys, got my boat about finished up. Took it to the lake and played for a couple days. Think I need a different prop. Im running 34 mph (GPS) at about 4700 RPM. I feel like the boat needs a little more push out of the water. Was thinking about a four blade prop to help with hole shot and keeping on plane at lower speed. By the numbers on my current prop I cant tell what pitch it is. But in comparing it to another 15 inch pitch it looks the same. So I'm pretty sure it's a 15, stainless. I know I need to get my RPM up. I think that will help with gas consumption also. By the way the boat is 21 ft and motor is a 74 Johnson 115. Anyone else with a similar setup? Can anyone offer any advice? Thanks in advance.

 

[1973Chieftain]

I would doubt it's a 15 pitch. Have you tried googling and of the numbers? My set up is a bit different, but I've used 17"-21". I would have thought you would need about a 17" for that set up

 

[eckhoffb]

I have tried searching this prop. it has three sets of numbers. L574. 420A. and W737
Thats the only markings i can find on it. I have a friend with an '73 85 hp with the exact same prop. Those are the only numbers we can find on his too

 

[Watermann]

All of the props I've ever had show the diameter and pitch stamped on the prop hub. Although not all are there, do you have the prop off of the shaft? If not take it off and see if the stamp is under the prop washer.

Sluggish out of the hole and lack of RPMs at WOT usually means that the pitch is too high for the set up you have. Dropping 2" in pitch should put you up over 5k in RPMs and increase the speed of the jump from the hole.

 

[eckhoffb]

ok I finally found the numbers. It's a 13 3/8 X 17. part number is 384139. What would a 13x15 solas four blade do for me. Would it get my RPM up and have better hole shot

 

[jbcurt00]

You need to check the prop chart for your motor, just because it has a 13.375 X 17 prop on it currently, doesn't mean it's the ideal prop for your boat, motor & usage combination. And by changing diameter & pitch to a 13 X 15, you may or may not be getting the optimal prop either. Same for changing from a 3 to a 4 blade, may or may not help.