three or four blade?

[fatmako]

I have heard conflicting theories regarding three and four blade props. My current rig is a 26 ft. single diesel inboard (135 hp. approx.) which is turning a 17 X 17 three blade. I am not happy with the performance (15 knot cruise, and cannot carry a load) and I think the prop is to small. I have tried larger three blades without much success.

I was considering going to a somewhat bigger (17 X 19) four blade as I have been told that a four blade prop boosts your cruising speed. Any suggestions?

The boat is a Strike and weighs approx. 5,000 lbs. I know it sounds like I'm a little short on horsepower, but several people have told me that with the torque produced by my diesel, I should be able to sustain a 18-19 knot cruising speed once I get her propped right.

[OUTCAST1]

Check this website: The boat is a 26 ft. Strike with a 165 HP single diesel. Note that even with the bigger engine, the cruising speed is listed at 13 knots, with a max at 18 knots. If you're cruising at 15 knots with the smaller engine, you might be pushing that engine too hard already (more fuel consumption, quicker rebuild.) You can throw all the money you want at re-prop jobs, but on the surface it looks like shooting for a 18 knot cruise with that boat and that engine is frivolous. If you're in a hurry, sell it and buy a faster boat.


http://www.yachtworld.com/core/listing/pl_boat_full_detail.jsp?slim=quick&boat_id=1438679&ybw=&units=Feet&currency=USD&access=Public&listing_id=23264&url=

[fatmako]

Thanks for the reply Outcast. Actually, I had seen that boat on
yachtworld a while back and was a little surprised at its slow cruising speed. Even with my current prop, I am able to cruise
a true 15 knots without pushing the engine. Top speed is 19 knots. I am only looking to gain two knots or so at cruising speed
which is why I was considering the 4 blade.

I know with older diesels, sometimes its hard to determine the actual horsepower rating. Perhaps that other boat is actually rated at less h.p. than they think. Mine is a TMD 40b which I have been told is somwhere between 135 and 165 h.p.

[FinaddictMike]

A 3 blade is for you. The 4 blades are for the 17' 225hp demons that hole shot 0-60 in 5 seconds. You don't need that much bite.

[Sandtiger]

And of course hull design has a lot to do with speed also.........[wink]