to hydrofoil or not to hydrofoil

[Ranger330]

Heres my stats. 17' Ranger 330V with 90hp Evinrude
prop 13x19 SS
40 mph @5300 rpm WOT (this is without the hydrofoil)
38 mph @5100 rpm WOT (this is with the hydrofoil)
Without the hydro it takes about 8 seconds to get on plane
with the hydro it takes about 3 seconds.

Would a prop change possibly allow me to get rid of the hydro and keep my hole shot?

 

[walleyehed]

Drop to a good quality 17P SS such as a turbo1 and with vent holes and the better blade design you will gain better holeshot AND get the rpm up to at least 5800 where it should be.
You may possibly need to raise engine if mounted on the transom and not a jackplate as well.
What SS prop model are you running now??

 

[Starcraft5834]

4 blade= best hole shot

 

[Ranger330]

Looks like an OMC prop. Maybe the one that came on the motor. The tag on the motor says B.I.A. 90hp at 5000 rpm. Range 4500 to 5500. Should I be turning 5800?

 

[Starcraft5834]

No. You need more pitch. 1 inch pitch increase should reduce rpms bout 200.. a 4 blade in proper pitch will optimize hole shot..However. your top end speed will go down 1-2 mph

 

[Starcraft5834]

Lots of folks want great hole shot and top end speed.. kind of like wanting your cake and get to eat it too.. 3 blades best top end speed. 4 blade gets u best hole shot. . Pick what cake u want...

 

[Ranger330]

So what about the hydrofoil? Should I find the right prop and take the hydrofoil off? I have great hole shot with it on, just lost 2 or 3 mph on top end. Does the hydro stress the transom at all?

 

[Starcraft5834]

Stress transom..no

 

[Starcraft5834]

Your performance numbers w foil are ok..just keep it. .

 

[Ranger330]

Thanks for all the input guys!!

 

[Sea Rider]

Try distributing your deck weight evenly or moving some up front, go full throttle and check if planes faster than planed out as before.

Happy Boating

 

[Mi duckdown]

40 mph @5300 rpm WOT (this is without the hydrofoil)
38 mph @5100 rpm WOT (this is with the hydrofoil) That should tell you something. your rpms are too low for that motor

 

[Ranger330]

What should my rpms be? Operating range is 4500-5500.

 

[steelespike]

Slip seems a little high 16% without foil 17% with foil.
Is your speed by a gps?The 2 most suspect gauges are the tach and speedo.
I think 5300 is reasonable with the 19" prop. Perhaps the speedo is a little low.
​ Seems unlikely a ss prop would have high slip.
If the foil is eating 2 mph its eating speed through the entire range.Yes it probably allows slower cruising speeds but at what throttle position?
If you go to a 17" pitch ss it may add 400 rpm.Hole shot should improve should stay on plane at reduced throttle with less fuss.
top end may be a wash at about 40.None of this is carved in stone.

 

[Ranger330]

I agree steelespike. I think it will be worth purchasing a 17 pitch SS and pull the foil off for a test drive. I'm using GPS for speedo. The tach is probably the one that came on the boat 1988 model. That would possibly put my rpms at 5600 WOT.

 

[walleyehed]

What year 90 is it?? 60 deg or 90 deg??
If it's a carbed engine, 5500 is minimum target for 60 deg looper. if it's a 90 deg crossflow 5800 is minimum target. Been down this road a million times.

 

[walleyehed]

What year 90 is it?? 60 deg or 90 deg??
If it's a carbed engine, 5500 is minimum target for 60 deg looper. if it's a 90 deg crossflow 5800 is minimum target. Been down this road a million times.

 

[Ranger330]

It's a 1983 90hp evinrude. It is a carb engine.

 

[jestor68]

If the ID tag on the motor says 4500-5500 rpm, I'd go with that.

A Trophy Plus ( 4 blade )17 pitch without the foil should be about ideal. Good hole shot and good bow lift.

 

[walleyehed]

1983...It was designed to run on fuel of that era (Good fuel) and what we have today is crap compared to that. Your engine is a 90 deg crossflow and we've found in many, many cases and several years of testing, these engines run best when propped and set up for 5800 rpm. 5000 will load your ring lands with carbon, raise exhaust temps considerably higher than they were ever intended to run (again, due to the crap fuel we have today). That engine is 31 years old. it does not act the same on the fuel that we have today plain and simple, and yes, you will get many opinions but if you were able to ask anyone on this forum that knows my history they would tell you my tech advise is good and based on 40 years working and racing these Johnrudes. The hydrofoil is a "tool".....some tools are Band-Aid fixes for underlying issues. On a platform such as a bassboat, this is one of those issues. It comes down to what do you really want from this rig. You can run a 1000$ prop on this and still have the same problem. Are you willing to raise engine or possibly install a jackplate? Are you willing to test several props of different blade geometry to find the style that best fits your use desires? 3 vs 4bld?? $bld is always going to lift the stern more and will always have more wetted boat surface at high speed resulting in lower top speed. If you are willing to except speed loss, that's fine, but if youre willing to raise engine (4bld requires higher engine mounting height for best efficiency), you may gain some speed back but it will not be as good as the proper 3bld and correct set up. It really all comes down to the bottom line of what you want.