I Need Some Advice Guys

[196thDLR]

I'm sure someone out there, has, or, is using hydrofoil wings that bolt to a cavitation plate. Are they worth the money, and, do they work? I run a 1992, 1775 Lund Pro-V with a 2003, 75HP, 4-Stroke. Gererally, 2 two hundred plus men and all equipment, full tank of fuel {24 Gal} and will plane out at 33.6 to 34.5 SOG @ 5400 rpm's.

[ChuckN]

I have seen them work and I've also seen where they did not.

An old Glasstron runabout with a 50hp motor did improve performance, mainly planing up.

I bought a 17' Alumacraft with a 115hp and the previous owner installed the fin. It slowed the boat down (didn't need it anyways).

I personally think that speed is not too bad with that scenario. The fin might help with getting the boat on plane quicker, and that's about it IMO.

[Rost]

What goal are you trying to accomplish? More speed? Better Hole Shot? Better fuel economy? Looking at your post makes me think you are trying to get more speed. A few plates out there claim to boost speed, but I rarely hear of guys buying one just with hopes that it gives them a few mph. Usually people buy hydrofoils to improve their holeshot. For the speed part, they usually get a stainless prop.

I don't think your speed is all that bad for the rig you have. My 18' Tourney Pro W/ 75 hits 30-32 w/o stainless prop.

[marine_man]

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What goal are you trying to accomplish? More speed? Better Hole Shot? Better fuel economy?

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I'm going to guess you're looking for better holeshot, given the low RPM you're getting at top end. What brand 75HP 4 Stroke are you running? Most 75 HP four strokes upper RPM limit is 6,000 RPM and you're about 500 RPM short of that, which means to me that you're running a higher pitch prop than what you could be running (which would get you better holeshot). The downside to this is that you will loose some speed...

IMHO I think the hydrofoil / whale tale, etc is a band aid for a propping problem. In the right application though they're just what some people are looking for. I guess they're cheaper than a new prop.

So, as Rost said, what's your goal, and what brand motor are you running?

marine_man

[New Yankee]

Had one on a bass boat that tended to have problems 'porpoising' due to the weight of the motor vs hull. Helped that out and gained a quick hole shot. Speed not affected either way, but much better control on plane.

The best thing I've had on a boat was hydraulic trim tabs, you gain a bit of speed trimed out and the control and ability to compenstate for different loads was great. There is a new product called smart tabs that many tout, I've not had them but they have a dedicated following.

[Valv]

Marine_man is correct, your WOT RPMs are a little low, I wouldn't go any higher pitch, if youa re trying to get more speed I don't think you can do much, but talk to a reputable prop shop.

If you need more holeshot you will have to get a smaller pitch but you will loose speed.

You have a heavy boat, the 75hp is probably the lowest you can have with that boat, if you need a lot more speed you will have to upgrade to at least 115hp.

I wouldn'y recommend hydrofoils, the term "band aid" fits perfectly.

[Northlander]

I agree a 75 4 stroke may be pretty underpowered for that boat. A 90 or 115 would be great on there. A 115 4 stroke would be nice. I dont know if you could go any bigger on a 4 stroke due to weight Verses horsepower/speed payout. I know its not the cheapest but I think you could do a lot of trading out of props only to find out what you really want/needed is a bigger motor on that boat. Just my 2 cents worth is all.

I run a 1700 Explorer with a 115 Yamaha 4 stroke and only get about 42-43 mph with a full load and 1 other guy. With a 3rd guy Im around 40mph on the GPS. As said above going lower pitch will get you out of the hole fatsre but top end may suffer a bit. Maybe try to cup the prop you have now. A good prop guy can do this easy. Jay Soderbloom did one of mine and put some exhaust holes in it and it really helped out. Better hole shot and didnt lose any top end speed. Plus it holds better inturns now.

[196thDLR]

I am now going to try and answer all of your questions. The motor is a Yamaha, tiller. The Coast Guard plate states 75hp is the max. This I do not understand, because the boat alone, nothing in it, weighs 1188 lbs.

What I am looking for is the best fuel economy that I can get. With the price that non-oxi fuel will run this year, I will need every 1/10th of a mile I can get from a gallon of fuel.

The prop is the original prop that came with the motor when I purchased it. No SS prop on this one. I fish where there are too many rocks.

I do not run my motor, round things, to the wall, at least not for any length of time, max 45 seconds.

I put a very good coat of marine wax on every fall and again in the sring.

Hope this helps, fella's.

[Surface Tension]

A fin will get you on plane faster. You still should be trimming in for hole shots and once your on plane, you trim up. You won't go any faster with the fin but you will be able to stay on plane at slower speeds. So if you can stay planed out with less throttle, thats going to save you money, a lot of money.

Dropping down in pitch will give you a better hole shot and usually take some top speed off but considering how your RPMs are low at WOT you might find out your overall performance is going to increase and possibly your speed if you drop down 2 in pitch.

[marine_man]

The other benefit of changing props is you will be running your engine where it was designed to run, and won't be lugging the engine at the lower RPM.

I'd seriously consider dropping 2" in pitch on the prop.

In order to find out what pitch prop you're currently running you'll need to take the prop off and look inside the front side of the prop (front being front of the boat) and you'll find some numbers stamped there , likely 13 X 19, or something along those lines...

marine_man

[196thDLR]

I want to thank all of the members for the responses. I truely appreciate each one.

ChuckN: On the main street of Clitherall, at least what used to be main street, East end, there used to be an old false fronted building. The cement in front of that building has a imprint of a horseshoe in it. My father had a blacksmith shop in that building during the 30's and 40's. I went to kindergarten, 1st and 2nd grade in Battle Lake. All of my brothers and sisters graduated from Battle Lake.

Rost&New Yankee: My brother-in-law was stationed in Madison. He was in the SD Highway Patrol. During the early 80's I lived in Sioux Falls in a sub-division off of West 41st on a street named West Masa Pass.

Valv: When you see Ben S. at the lumberyard, please give him my best. My wife and I were neighbors of Ben and Janice in Lonsdale for 6 or 7 years.

Marine-Man: I do know where Lisbon is, but know no one there. Thanks again for your reply. What prop pitch do you suggest?

North&Surface: I have read a great many of your posts over the last few years and have enjoyed them very much. You know what you are talking about. Suface, I even know where Twig is!

Thanks again fellas'.

[upnorth]

I have heard of people using those things when their boats handled poorly and it seemed to have helped them. Another thing to remember is that every extra thing you put in the water on a boat will create extra drag.

[marine_man]

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What prop pitch do you suggest?

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The answer to that question is going to be dependent on what pitch prop you have on it right now... I would guess, without knowing your current pitch, that dropping it by 2" (from a 19 to a 17, etc) would get you back up into 6,000 RPM... but it's hard to say without knowing what you have right now.

marine_man

[cold one sd]

I had one of these on one of my boats. They seem to get you on plane faster and keep you on plane at lower speeds. This alone should save on fuel. I don't believe it made a difference on hole shots or top end. The boat I had it on was an inboard/outboard and was a bit rear heavy.

[ChuckN]

Hey 196, a lot of the old buildings are definitely there...can't recall that one off hand, but will have to look. Some people have made residences into some of the old buildings (like the old bank on the corner).