Cat 3126 1:1.5 gear 24x26 4blades

[Nawty1]

Looking to get more speed and less prop wash on my 40ft boat.
3126 cats 450hp
1:1.5 gear
1 3/4 shaft with 24x26 4 blades.

I cruise 24knts top out at 30 and have moderate wash while trolling.

Would love to hear if anyone has any ideas on how to get

more speed / agressiveness
less propwash....

Or if anyone has or knows anybody that has a 40 Ocean with 3 blades I would love
to hear how they like or dislike them.

I like my setup but am always looking to tinker around......

[seapower]

Not really sure of what you're asking here. Do you have enough clearence above the prop to swing a larger diameter prop? A different gear ratio would allow more diameter. If you're breaking the surface with excessive prop wash, I would tend to think your looking at hull design and shaft angle. In the end it's all thrust. May play with some different stlye prop's, diameter X pitch, number of blades, etc..... If you're gonna re-invent the wheel, break out the check book. In the end I wouldn't know what to suggest, without seeing the hull, shaft angle, prop clearence and most importantly, what you are refering to as excessive prop wash. Frank

[Nawty1]

It is not excessive prop wash.....Just looking to clean it up. But that is the last thing. I want more speed....and for it to be more agressive. I dont know much about drivetrain on boats , just wanting to learn and tweek !!!! It really runs great now. Hits the manufactures numbers dead on the nose. 24knts @ 2400 rpms and top 30knts @ 2800.....Engine dead revs upto 2800.
The boat is a 40ft 1997 Ocean. Just looking to see if anyone else has tweeked or has run 3 blades and if so what size ?????

[seapower]

If you have 4 blade prop's on now and go to a 3 blade prop, the general rule of thumb is that you'll be able to add 1 more inch of pitch. That will give you abit more speed, between the additional pitch and 3 blades. But on the other hand a 3 blade prop isn't as smooth (less vibration) as a 4 blade. You can play with the prop's you have by adding "cup", if they don't have it now. Do know that if you add cup, you're gonna have to decrease pitch, so that you don't overload your engine's. Your engines need to be able to run loaded at rated RPM. Good luck, Frank

[tom s]

I have found with WAY to much money invested that 3 againt 4s the 3s are faster on the topend but the 4s were a touch faster at the cruise RPMs and were almost always smoother.My new boat has 2 1/2 reduction and the wake is way cleaner.FWIW,Tom

[PacificBlue]

4-blades will give you more "grunt" at cruise as well as in a heavier sea. It has amazed me in the past how production builders spent little time in selecting the optimum propeller, with cost usually the driving factor. This is were it get's tricky and potentially expensive for the boat owner - there are better props available then the ones you are running and how do you find it? You need a highly reputable prop shop to start the process, but I would go to the Miami Boat Show and hit alll the propeller manufacturers (and their reps) hard. Ask them if they are willing to meet your requirements and if they don't, they take the propellers back. A confident manufacturer should be up to the challenge in these tough selling times, so hopefully you may be out of pocket two haulouts at most.

At speeds of 30 knots, you don't need to go for the highest end props like Veem, but you can definitely look at ZF, Acme, Hung Shen and some Michigan Wheel. I have been able to test 5 - 6 different props on one boat model many times before, and you will find differences between acceleration, cruise speed, top speed, and smoothness. Ultimately, you are locked into a gear ratio that drove the design for your shaft angle and propeller clearances, and if they did not base the ratio selection for optimum diameter and blade loading, your wiggle room for improvement may be limited. Ask the prop guys if you have sufficient diameter and what the blade load is for a 3-blade propeller, then determine how much $$$ you are willing to risk

[rmbates]

Before you go spending money on new props I would suggest you take a closer look at the propellers you've got.
How many rpm's are you getting at WOT? How is this being measured? If you are taking your numbers from installed tachs you could be making a big mistake as they are notoriously inaccurate. Check WOT rpm's with a phototachometer for a number you can trust.
Once you have this data in hand pull your props and take them to a reputable prop shop that specializes in computer tuning. They would have either a Hale MRI or a PropScan propeller measuring device and can tell you the accuracy of your props relative to ISO standards (most do this analysis at no charge). If your props are not at least an ISO Class I have them tuned to this level. Sometimes this in itself can produce more speed and is really the least expensive modification you can make to show an improvement. If this isn't sufficient and you feel like opening your wallet then you could check out 3 bladed props. I would definitely opt for CNC machined propellers from someone like Hung Shen or ZF as they can be ordered in at Class S or I where this is generally not the case with production props. While you may have to wait for up to 8 weeks, the benefits of CNC machining is accuracy and more uniformity in blade thichness. The key to all this is to have accurate data going in and to find a reputable prop shop that will steer you in the right direction and not produce false expectations. Fact is, you're delving into the trial-and-error world unless you've got hard data from an identical application....and it can get expensive. Good luck!

[Russell A. Jost]

Nawty1, before you spend a ton of money on new props, haul out, and retuning new props, there is one more piece of info you should have. You stated you have 3126 cats, these are the electronic controlled. You should have an authorized cat mechanic connect there computer to your engines and go for a test ride to find out what percent loaded your engines are at full trottle. For example, if they are 99 to 100% loaded at 2800 rpm you are not going to gain much with new high end props. But on the other hand if they are (lets say) 90% loaded then you might be able to pick up a knot or knot and a half by adding cup to your existing props. PS more speed equals more fuel. Good luck.