Four blade prop

[dngharvey]

1998 115 two stroke on a Scout 185 Dorado. Enjoy the package but wish it had more grunt out of the hole especially when loaded heavy. Tops out at 5800 and 40 mph, that's great but seems sluggish getting going.
Anyone try a four blade on a similar setup? Love to know the results.
By the way, trim tabs helped but could still use additional thrust.
Love this site and come here every day!

[rodbolt17]

your under propped.
max RPM should be about 5500.

try a prop with vent holes.
let the prop slip a bit while the motor is spooling up.

[dngharvey]

your under propped.
max RPM should be about 5500.

try a prop with vent holes.
let the prop slip a bit while the motor is spooling up.

Thanks, rodbolt. Always value your input. Guess that was part of my thinking process, 13 1/4 X 17 three blade SST now, if I went to 15 pitch it might give some grunt out of the hole but probably over rev even more. Just wondered if a four blade 17P might work to reduce peak rpm and add some low end thrust.

[99yam40]

Rod said you were under propped not over, so why would you drop the pitch instead of upping it?

Not sure what a 4 blade would do though, might find a prop shop that can help and let you try some out

[bajakeith]

Yikes !!

Your over propped,, by 2 in's.. a four blade will give you more bow lift in most app's... stay with a three.... figure 200 rpm for each inch of pitch...and those Scouts have abad gas tank habit....To say the least !! If a ocean boat ,,,forget about vent holes.. not good in a fallowing sea with load.,.

[dngharvey]

Thanks all, going to borrow a 19 just for laughs and giggles. I'll let you know what results.

[boscoe99]

Unless my eyes are playing tricks on me rodnut suggested that he is under propped. Under as too little pitch.

The WOT RPM redline for the OP's motor is 5500. If he is turning 5800 at WOT he is under propped.

[99yam40]

I fixed my post,
too many cold ones I guess

I saw there was a problem with the way he was headed , but my fingers or my brain did not write the correct things

[dngharvey]

I'm 70, lotta things don't work right these days, but boats are still fun.
Think I'm on the right track, higher pitch number = lower WOT rpm's, conversely, most likely less thrust out of the hole. That 5800 was with half tank and me alone stretching the rods for a few seconds.
Was maybe hoping to find someone who has tried the four blade thing and whether it made any difference.
It really is not that horrible, just takes a bit to get over the bow wave, and like most of us, just like to tinker.

[rodbolt17]

4 blades typically give decent stern lift.
mostly cause your now dragging a 4th blade in the water.

try a prop with vent holes, that should improve the hole shot.
that's why they are vented.

[99yam40]

might want to web search for Propgods and their forum.
I am sure you can find all kinds of info there

[RayBersch]

I have switched from (stainless) 3 to 4 on my F150 (Skeeter SL190) but my goal was different than yours. I wanted greater stern lift out of the hole and lower on-plane speed because I was towing youngsters. I had to play a bit with the pitch to get the 6,000 rpm needed for the F150 but got it right - I would have to look up the prop numbers to give you a comparison, which I can't do now. I am satisfied with the choice and accomplished my goal. But I also did not have a complaint with the 3 blade hole shot and I think your issue is more with the horsepower than the prop. A quick search for your boat showed a hull dry weight of 1450 lbs and my Skeeter is 1500 lbs so we are close. (though my 4 stroke probably weighs a lot more than your 2 stroke) Our hulls may be slightly different 'cause mine is more bass boat than bay boat. My top speed at 6k is about 56 gps with the 4 blade and 58 with the 3 blade - lightly loaded - I never try top speed with others in the boat.

I considered a F115 for my boat when I bought it new but ultimately decided it would be underpowered and I believe I was right because the 150 is noticeably slower all around when the family gets in for water skiing.

[rodbolt17]

and ALWAYS member.
2 stroke smokeys fire EVERY time the piston comes up, 4 stroke green motors, every other time.
makes a huge difference from idle to WOT.

[RayBersch]

rod bolt - point? OP is unhappy with 115 2 stroke, I am happy with 150 4 stroke - bet he would be ecstatic with a 150 2 stroke!

[zenoahphobic]

rod bolt - point? OP is unhappy with 115 2 stroke, I am happy with 150 4 stroke - bet he would be ecstatic with a 150 2 stroke!

Agreed. Why would a fourstroke be inferior, they generally have a larger volume to equivalent twostrokes to compensate for torque at the same HP rating?