Hydrofoil

[Jayfishin 63]

Trevor,

What do you think of a hydrofoil add-on for the outboard? ie. "Stingray"

I had one on my last motor and it think it made a big difference getting the boat out of the water and handling was better BUT it did seem to slightly reduce my top speed.

Thoughts?

Jay

[arvey 154]

jay

i was having trouble with my boat porpussing the motor would be all the way down and it would still do it. the power trim was useless tried to trim out and it got worse.so i put one on and that was the end of the problem trims out just nice.

arvey

[Some Old Guy 968]

I have a hydrofoil on my boat. They make a big difference for planeing out. The porpoising settled down too. The only thing that I don't like is when I'm trimmed out and have to turn suddenly and sharp the prop cavitates and over revs the motor. If you know you are going to turn sharp you have to drop the prop deeper into the water so it doesn't cavitate.

Roger

[Bottom Bouncer 22]

Roger I'm surprised that you have one. I figured that 75 Merc. on your Princecraft would just jump out of the hole. I always thought these "Stingrays" were effective on under powered boats. Something that I have done to my boat was raising the motor off the Transom by about 2 inches this was a great move. I also installed a Troll-o-Matic on my 75 Merc. Tiller to slow down the motor so I can troll with the big motor. Slowed my motor down from 3 miles an hour to 1.5.

[Bill Arnott 2]

Cheapest upgrade for getting up on plane. These will also allow you to run at slower speeds without having to play with the throttle constantly. Had one on my old boat(17ft walk-thru w/75hp) and it made all the difference.

>Bill

[Trevor Zimak 171]

I have a hydrofoil on my boat. They make a big difference for planeing out. The porpoising settled down too. The only thing that I don't like is when I'm trimmed out and have to turn suddenly and sharp the prop cavitates and over revs the motor. If you know you are going to turn sharp you have to drop the prop deeper into the water so it doesn't cavitate.

Roger

Rog, Avery

The reason you are experience porpoising is becuase your motor height is set too high and is also the reason you have to trim down while cornering. I would be interested to see if you still had this problem if you dropped your engine height one hole.

However, porpoising is common if your boat is improperly balanced; a lot of the time porpoising is a basic balance issue. It can often be minimized by trimming the motor down, which you have described. This runs the prop at an upward angle lifting the stern and pushing down on the bow to keep it from bouncing up.

The problem with doing this is that you are not getting full forward thrust efficiency out of the prop when it is at an angle. This causes both loss of speed (at any given RPM) and reduce fuel efficiency.

[Trevor Zimak 171]

Trevor,

What do you think of a hydrofoil add-on for the outboard? ie. "Stingray"

I had one on my last motor and it think it made a big difference getting the boat out of the water and handling was better BUT it did seem to slightly reduce my top speed.

Thoughts?

Jay

Jay,

A hydrofoil can do many things for you depending on your boat and setup numbers. For example, you have to consider the height at which your engine is running at. If your cavitation plate is below the water while at WOT you WILL lose top end becuase the hydrofoil will create added drag. Which would explain the loss of speed you are experiencing. Consequently, if it is above the water, there should not be no loss in top end nor is there rarely any gain.

Adding a hydrofoil will improve hole shot immensely and will also allow you to stay on plane at a lower speed. I would recommend adding a hydrofoil if you use this boat for pulling waterskiers, tubing, etc; simply becuase it puts much less stress on the motor.

[Some Old Guy 968]

Move it down one hole? How do you mean?

Roger

[Trevor Zimak 171]

Move it down one hole? How do you mean?

Roger

Mercury's have a 5 hole bolt pattern. If you look at your engine's mounting, it is probably in the 3rd hole. Try moving it down to the 2nd. You would have to unbolt the 4 bolts while using a motor lift and rebolt it back to the transom in the 2nd hole.

[arvey 154]

trevor

i'll have to check were mine is. like i said though mine did it when the motor was right down and yes i lost performance,and the power trim became useless.when i put the stingray on that changed everthing,i could trim the motor up and the boat would plane nicely gained speed and performance.

thanks for the info

arvey

[Trevor Zimak 171]

Arvey,

Just wondering what kind of boat and motor you are running? Depending on the application sometimes a hydrofoil can correct these issues, especially on smaller sized boats and outboards; 16' ish. Hydrofoils only can sometimes actually help to stabilize these smaller boats becuase they are lighter and more compact. By adding the stingray it may actually be balancing whatever is causing the porpoising. Or it could quite possibly be giving you that little extra inche or so of hull lift, which would explain the gain in speed. Other than that... i'm stumped on that one.

[arvey 154]

Arvey,

Just wondering what kind of boat and motor you are running? Depending on the application sometimes a hydrofoil can correct these issues, especially on smaller sized boats and outboards; 16' ish. Hydrofoils only can sometimes actually help to stabilize these smaller boats becuase they are lighter and more compact. By adding the stingray it may actually be balancing whatever is causing the porpoising. Or it could quite possibly be giving you that little extra inche or so of hull lift, which would explain the gain in speed. Other than that... i'm stumped on that one.

i have a 15' alumnicraft with a 40, i would have to say your right, soon i was able to use the trim you could tell the diiff.

not alot, but tlike you said that extra lift did help with a little boust in speed.

arvey

[Bottom Bouncer 22]

Move it down one hole? How do you mean?

Roger

Roger I understand your confusion especially if your motor is currently sitting on top of your transom, because your motor is not going down. But it will go up, my motor is currently sitting about 2 inches above the transom leaving a gap, making the motor look like it is in mid-air. That's why I pass you with the same hp. Most people believe the top of the transom is supporting the weight of the motor when in fact the bolts are. Like I said my motor isn't touching the top of the transom.

[arvey 154]

correct me if i'm wrong, is there suppose to be a certain distance between your inlet were your water pump is and the bottom of your transom? like 1 inch. you see if you lift your motor to high when your wide open you won't draw water.

arvey

[Trevor Zimak 171]

Roger I understand your confusion especially if your motor is currently sitting on top of your transom, because your motor is not going down. But it will go up, my motor is currently sitting about 2 inches above the transom leaving a gap, making the motor look like it is in mid-air. That's why I pass you with the same hp. Most people believe the top of the transom is supporting the weight of the motor when in fact the bolts are. Like I said my motor isn't touching the top of the transom.

Rog, how many inches is your motor sitting above the transom. How far is your prop shaft below the pad/hull of your boat?

[Trevor Zimak 171]

correct me if i'm wrong, is there suppose to be a certain distance between your inlet were your water pump is and the bottom of your transom? like 1 inch. you see if you lift your motor to high when your wide open you won't draw water.

arvey

There is no real distance, but they should be under the waterline. The golden number is to maintain a minimum of 15psi of water pressure while at WOT. However, you would need a water pressure gauge in your boat in order to know this. Mercury does make plugs that you can use to plug holes that are above the water line while at WOT, this way those top holes are not sucking air. I had the top two holes plugged on my last bass boat and they worked great. Water pressure increased because there was no air being drawn in from the top two.

My other suggestion Rog would be to try a stainless. A stainless is much stronger and will grab more water while making a tight turn and would cut down on cavatation.

[Bottom Bouncer 22]

correct me if i'm wrong, is there suppose to be a certain distance between your inlet were your water pump is and the bottom of your transom? like 1 inch. you see if you lift your motor to high when your wide open you won't draw water.

arvey

I believe your cavitation plate and the bottom of your transom should be level. In my situation my 75 merc. fourstroke will lose water at full speed if the motor is raised to high. But when I'm wide open I can look back and see my cavitation plate just above the water.

[Some Old Guy 968]

You pass me because your motor is two inches higher? Ummm Look at my partner compared to yours! HA HA HA! JK~

Roger

[Bottom Bouncer 22]

You pass me because your motor is two inches higher? Ummm Look at my partner compared to yours! HA HA HA! JK~

Roger

That's funny and True

[Guest Walleyer]

I just put a stingray on my motor ( 25 merc sea pro on a 14 crestliner deep and wide) and have noticed a big difference in the amount of time it takes to get on plane with a boatload. I've heard all the pros and cons to having a stingray on and I'm pretty happy with mine. The only other difference I've noticed is the drop in top end speed but I can live with it.