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

[ToneDef]

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

I've got a jack plate which allows me to raise the engine to the point where my prop shaft centerline is in plane with the bottom of the boat (if I wish to go that high) as well as adding 4" of setback to address the engine height, and I am waiting to hear back from Bob's Machine on a nose cone/low-water pickup to address the issue of drag and water.

I am actually relieved to hear that a good SS prop is in that range, I was worried I would be looking at $600+

As far as the (relatively) small MPH gains being worth it, to me they are. I came into this build with one goal in mind: 50 MPH. Will I make it to that? Probably not. But am I willing to do everything I can to get close? Hell yes. If that means dropping some coin on a good prop that's designed for this application rather than some stupid fishing prop, so be it. I suppose I probably am better off running what I've got first to establish some sort of a baseline.

Sorry if I came of as a bit of an *** before, that was certainly not my intention.

[capnzee]

It would be helpful if you would show us a picture or two of your project. Sounds like you are willing to put a few bucks in it--too bad you didn't take a look at APBA before you started building. Your aluminum prop is fairly easy to "work"--you may want to take a look at some of the stainless props used for racing and put a little "cup" along the trailing edge and just over the top of each of the blades. Don't get the cup too sharp or the aluminum will crack. Doesn't take much. Even though you don't have an APBA class to run in, Mr. Ron Hill is planning a "mini-enduro" scheduled for this fall, perhaps your boat will be ready and up to speed by then--I am sure that there is a class your rig will fall into! (that is if you have any racing in your blood-line--lots of guys simply like to ride around and think they are going fast--others like to prove it--which one are you?) Not trying to be a smart a**, just had my fill of "river racers" who like to talk big and sport a lot of t and a but are afraid to go chine to chine in a sanctioned race! RD

[ToneDef]

It would be helpful if you would show us a picture or two of your project. Sounds like you are willing to put a few bucks in it--too bad you didn't take a look at APBA before you started building. Your aluminum prop is fairly easy to "work"--you may want to take a look at some of the stainless props used for racing and put a little "cup" along the trailing edge and just over the top of each of the blades. Don't get the cup too sharp or the aluminum will crack. Doesn't take much. Even though you don't have an APBA class to run in, Mr. Ron Hill is planning a "mini-enduro" scheduled for this fall, perhaps your boat will be ready and up to speed by then--I am sure that there is a class your rig will fall into! (that is if you have any racing in your blood-line--lots of guys simply like to ride around and think they are going fast--others like to prove it--which one are you?) Not trying to be a smart a**, just had my fill of "river racers" who like to talk big and sport a lot of t and a but are afraid to go chine to chine in a sanctioned race! RD

Heh I hear you on the "all show no go" guys but I'm a racer through and through, from BMX as a kid to bangin' bars on the motocross track currently, I like to prove that I can hang and hopefully I'll get the chance to do that with this boat as well. If she ain't good to go by fall, something seriously ain't right! A mini enduro sounds like something I'd definitely be interested in partaking in.

Here are a few of the most recent pics. I've got the bottom and side planking on now.

[capnzee]

It looks like you are doing a real nice job--got plans or are they in your head?
Looks like a shallow V up front to a flat bottom in the rear?? Be sure and get some good support on that transom--tie it in real good cause it is going to need a lot of strength to support that engine on a jack plate. Rod