Newb here with a question on props

[ToneDef]

Sorry if this is in the wrong section. I am new to the forum and I am building a small hydroplane. Unfortunately the design is not class-legal per APBA's definitions, but I see it as a jumping off point for what could potentially be a fun future in boat racing. I've got a Nissan NS15B2 for power and I am looking for a prop and was told that for this sort of application, a cleaver style would be best and he told me to check out Ron Hill Marine! Then I found this site and that Mr. Hill is the man here. Anyway the engine has a 14 spline shaft, thru hub exhaust, and wants to run 4700 min. RPM and 5500 max. RPM @ WOT. Mr. Hill, do you build custom propellers to suit any application? Would I be best off waiting until I have run the boat a bit (she is about 1 month to completion) to see what I'm looking at for MPH and then talking prop?

[Ron Hill]

Got lots of props for you and others with 14 splines. But may need to see the prop first.

Call me Ron, unless you are my daughter-in-law (LOL) or one of my nold students....

[ToneDef]

Thanks Ron. Here are some pics of the prop. It's 9.2x8.5

[ToneDef]

Ron what is the avg. cost for one of your props?

[ToneDef]

nobody?

[capnzee]

If nobody wants to step up here, I would suggest that a good stainless prop for your engine would come in at 200 to 350 bucks. (maybe less if the prop has been used.)This may be more than you want to spend on something that may add as little as 5 to 10 mph on your rig, depending upon what you have built. Before you can build the prop that you need, you will have to try what you already have (which isn't much), but it is a starting point. If your boat is in the building stages you may want to think about the transom height. With a planing type, low drag hull, you will get about 90 per cent of your total drag from the lower unit. The higher out of the water you can run your unit, the less drag you will encounter and the faster your boat will go--the problem here is two-fold. No.1, your engine is not built to run at a height that you would like it to--the water pick-up is simply too high and if you get the engine up where you like it, you most likely will not pump water and you will overheat. No.2, your present prop is not designed to run on the surface, or for that matter partially out of the water. Why don't you ask "Mr. Hill" if you can buy a stainless prop from him that is about the same diameter and maybe an inch or two more than your stock prop. I am sure that he will take the prop back in trade for another prop once you have tried it and have formed a basis for further testing. (this providing you have not dinged or screwed up the test prop.) Rod