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Hey guys another question, this is about props. My B31 has Cummins 6bta 250 HP. I swing 4 bladed bronze 20x23 Hy Torq light cup props. Every thing is good except around the dock. she has a tendency to lurch. My old B31 was gas powered so didn't have the torq. that I under stand. Would some one enlighten me on the difference in performance between three and four bladed props and would three bladed help .thanks again.....Russ

I cant speak to the 3 vs 4 blade part of it but what I did on my 3 blader was instead of adding pitch to get the proper rpm's at WOT, I added cup. The cup works at the upper end of the scale, when you want speed. Pitch made me move too fast at the low end (trolling, docking, etc.

Russ,

I think the lurching problem is all about your gear ratio and has nothing to do with the props. In my 33 I have 300hp B-series with 1.5:1 220a's with 3 balde props and I'm doing almost 6 knots as soon I put them in gear. I bump them in and out of gear all the time. It was a bit disconcerting at first, but now I love it and would never go back. Just line it up and bang, you're in the slip.

The 4 blades will bite more at idle then the 3 blades your in gear idle speed will be slower with 3 blades your cruise will be less efficient as a rule with 3 blades. Just learn how to drive the boat again, you will get used to it. I'll take a boat that moves when you put it in gear over one you have to throttle to move everyday

Welcome to the diesel club

I have 22x23, four blades, 300-6BTA's and when I was working on her a friend told me to be careful the first time I put her in gear, "cause she's going to step off smartly."
Sho nuf! At idle she does 3 1/2 knots which means she's a bit fast for striped bass. Guess I'll add trolling valves or at least one. Tried trolling on one engine dragging two five-gallon buckets, no difference.
Bump, bump, bump.

Mickey

See how bob Lico made out with his trolling valves before spending the money

I have the 4 blades. I carry alot of # and it really helps climbing waves on the way offshore. I dont troll for bass though.

What JP said; you'll get used to it and you'll get to where you are glad to have the "lurch".

Russ

I have the 20x23 DQX 4 blades in mine with the 270 Cummins. Yes she does lurch. If everyone is positioned right not a problem. When leaving the dock I usually put one in gear. Keeps the crew from going overboard. Or if you want to fix one of the crew, you could say, please just lean over the transom and make sure I am pumping water, then pop her in gear.

250 6btas 20x23s, what Tony said

Thanks every one, I quess it's just goingto be a learning process, spring is just around the corner...Russ

Try my ride I will show you the ultimate lurch. All cummins have a flex plate whereby some of the inertial torque is taken up by the use of springs. I have ZF Vulkan drive direct no springs. When the gears go in drive they go in no pussyfooting .i have three blade but the lurch is the same. Peter I have trolling valves on both gears but not really practical for docking. You lose propulsion both forward and backward . At one time I use to dock that boat with a minumim speed of 12 knots. Talk about lurch!!!!! Believe me you get used to it. When backing up into dock space you check wind,current and condition then let it rip ,three feet before hitting dock you slam forward, and don't drink!