Installing and Testing an Outboard Hydrofoil

In this video I install a hydrofoil on my boat and compare the before and after results. It helps get on plane more quickly and stays level. Hydrofoils can also help correct the bow riding too high, porpoising and propeller ventilation problems.

Dangar Marine

About Dangar Marine

MarineEngine.com proudly sponsors the Dangar Marine YouTube Channel. Our friend Dangar Stu draws on his experience as a commercial boat skipper and mechanic to make some great how-to videos. Dangar Marine videos cover a range of relevant topics in outboard repair, boat repair/upgrades and seamanship. Subscribe on YouTube to be notified when new videos are released.

Installing and Testing an Outboard Hydrofoil – Video Transcript

Hey there, Dangar Stu here. Today's video is about putting this hydrofoil on my boat the green machine and is proudly sponsored by Marine Engine com.

What I'll do first is just head over to the bench open this packaging up and we'll just have a quick look at the instructions on this particular hydrofoil is made by Stingray and called their Classic. I'll put a link to it in the description so you can find it if you look if one this one sold for 40horsepower and up. They come in various size brackets, the Honda on the green machine is exactly 40 horsepower so this is sort of at one extreme end of the bracket but we'll see how it goes. We'll go through the advertised features on the box too. So what it's saying is it will get a boat on plane in less than half the time. And although I've never been worried about how much time it takes to get the green machine on plane the sooner you get on the plane the less wash you make. Because when you first go from a displacement mode see in the water and taking off that's actually when you put out a fair bit of wash.

Depending on where you are that could be a nice side effect of putting this on is just making less wash. It says it's reduces valorize so allows the boat to sit level instead of the bow sitting up it'll bring the stern of the boat up. I'm not so worried about that because often with the green boat and actually struggle to get the bow up and I need to trim it high. I want to get the bow up in rough weather to keep the boat dry so we'll see whether it's sort of good or bad. In that sense it says that it stopped porpoising which is where a boat sort of does this as it goes green machine doesn't do that so not worry about that. Either. It talks about how it wipes out cavitation. I think it's more ventilation, we should write to them. Delivers true stabilization. I don't know what that means. Aids pulling skiers I don't do that. Saves fuel that's good. Before we do this install though I'll just show you some footage I took this morning of the green machine on the water without this hydrofoil installed. I don't have a trim tilt gauge on the dash of the green and I normally run with the trims all the way down anyway so I've never really had a problem with this boat.

A big part of purchasing a hydrofoil for many people it's sort of solving a problem the boat has. So in this case is not really a true test in a sense that the boat actually doesn't have any real problems but we'll give it a go anyway. What I'm going to do is trim the motor up as much as I can until it starts to ventilate and then I'll just have a look. And there should be some part of the outboard I can see and that'll give me a sense of how high it actually is trimmed up at least relative to after I put the Hydrofoil up. Before I do that I'll go grab Eddie to wonder dog because somebody commented the other day they've seen him on an intro and they haven't seen him in a video so I'll go grab him and he can help. Come on Eddie jump in.

Yeah so it's a pretty nice flat day today which is good. Perfect for doing these sorts of tests, you have to get lucky sometimes. what I'll do now is we'll just go down just do one run trimmed up as high as I can see if I can get some sort of way of measuring that. Then we'll do a few turns as well. I'll point the camera backwards as we're doing these runs rather than sort of talk the whole time and hopefully we'll be able to sort of hear when it starts to ventilate so here we go. All right you can hear pretty clearly when it starts to ventilate so what I'm going do is sort of basically sitting at my eye height. Now look back see which part of the leg I can see and use that as a judgment of how high it is and hopefully that'll be meaningful in some way. So I've marked a line on the leg of the outboard level with the transom bracket so I think with the boat sitting level in calm water that should give me a reasonably accurate indication to measure against of how high up it is trim now.

What I'm going to do now is do another similar run trim it up it starts to ventilate trim back down. Then we'll start doing a few turns. What do you think Eddie you do look like a drowned rat grow some hair back. So with it trimmed as high as I can without a ventilating in a straight line you only have to do a reasonably gentle swerve before the starts to ventilate again. So we'll see if there's any difference there as well. Although I mostly run with the boat trimmed all the way down there is one reason I like to trim it high and that's if it's a rough day, just to get the bow up to keep you dry. Rides nice it's or the waves and everything so if a hydrofoil allows me to trim the bow higher and not ventilate then I think it will work. See the jellyfish, I'll show you these got loads of these jellyfish at the moment go on Edie eat it hey leave it alone it takes me too seriously. He loves chasing anything in the water they're born fishermen. There are 2 main two tests I wanted to do before installing a hydrofoil. I know they're not hugely scientific but I do think it'll give me a good sense when I put it on of how different it feels. All right now we know what it was like let's go and pop it on the boat.

The instructions for the Installer are pretty straightforward. All they're saying is to put it on top of the outboards anti ventilation plate push it as far forward as the boat will allow or the outboard will allow, and then we're just going to mark it up for true it's actually got a notch here that keeps the center of the back and then in the front I've got these two corners. So they don't tell me whether I'm straight and true on the boat itself. Then I'll just mark for general holes. The back holes on this is slightly deeper so this pen hasn't reached through so I'm just going to grab a scribe. This is what we've ended up with these two holes are reasonably close to the back here we can't see over the glare and these ones are here. Because the Hydrofoil hooks in along here it's centered there. I know so I might just quickly measure the outside edge to these marks just to make sure I've got it on square. These marks are 14 millimeters from both sides so I think it's pretty good to drill.

I'll just mark all these with a punch so that the drill doesn't go wandering around. There's two makes of bolts in the kit they're short and a long so obviously the longer ones are going to go at the back where the hole is deeper on the plate. I'm just going to measure the diameter of them so I can pick the right drill bit. So they are six mill bolts a little bit over. I'll go grab the six mill a bit The bolts go all the way through into some Nylon lock nuts so I don't need to drill this too small and tap it or anything like that. So I'm just going t draw them the full six mil so they can push straight through Because those bolts came out at six point one millimeters I might find I need to go to a six and a half millimeter drill bit but I'll start with the six I can always take more out. [Music] Aluminum is pretty soft I'm not worrying about having oil and slow speed drill and all that kind of thing.

If I do a test fit on these bolts there's still a little bit tight you could definitely tap a thread through they're not too tight but the idea is they push through so I'm going to go up to six and a half mil. yes that's good now so six and a half it is. You get four rubber washers as a part of their mounting hardware and these go on the bottom side of the hydrofoil and then we pop this on and then our mounting screws go from the underside up. The nylon locknuts on top of these. The nuts fall down into a little recessed space. There so no washer or anything underneath that just straight in. Now I'm just going to trim the motor up to make it easier to get to the Phillips heads on the bolts from Underneath. No huge trick to tighten them up other than tighten them in a bit of a star pattern and don't over tighten them. Just let the lock nuts do their job. Doing these bolts up is probably easier to take the prop first but I'm just going to work around it. So now they're all run down just tightening them up in a bit of a star pattern it's kind of done pretty straightforward really. Alright next thing to do is go and take this boat back out on the water and repeat that test. Well here we are back on the water much later in the day obviously, I didn't actually do any quantifiable tests of how quickly the boat got on the plane before but I'll take a bit of a run now and just see if it feels any different.

One thing I can tell straight away is it doesn't feel like the bow lifts and then the boat comes on the plane. It actually feels a bit like it sort of lifts the whole thing much more sort of horizontally to the surface which is interesting because of that not having that phenomenon of sort of sticking the stern in first. It definitely I think will make less wash and maybe you did go on the plane faster because of that. That's never really worried me but it's interesting to feel it. All right now I'll do the same thing we did this morning which is run along. See how I contribute for starts to ventilate trim back down and start doing some turns. That's where it started to ventilate actually doesn't seem to happen as catastrophically. I'm assuming it will suck air around the sides. I'd say I could trim the motor up to about the same height as we did before and start turning, it's interesting you actually instead of getting this sort of sudden catastrophic ventilation you get it sort of sucking a bit of air that catches again.

And it feels like it sort of oscillates between ventilating and not a little bit so I guess you could call that an improvement. the most noticeable improvement for me really is just taking off in a straight line the boat stays much flatter as it comes on plane instead of going bow up. and I think that's more comfortable for people and puts out less wash and has less things flying around the boat. So I think that's definitely an improvement. One other thing I've noticed in the past when I've had these ventilation plates on is if you come into a wall or a vertical pile I also find they act as quite good prop guards. Just to stop the prop from knocking against a pile like that, dinging the prop and stall in the motor.

So I think that's actually a unadvertised benefit. But I actually think it's one that I notice more than the dynamic benefits. When it comes to the question if should have put one on my boat to me it comes down to does the boat have a problem, does it ventilate even when the motors trim down? In which case yes you probably need a long shaft or mount at lower position. If the boat porpoises a bit with a bow sort of bounces up and down that can be trimmed but maybe a hydrofoil will help you with that problem as well. I've also heard of people have had boats that just haven't run true in the water they've sort of got on the plane and it's not so much because of the sort of transverse thrust of the prop but maybe the hulls just not quite right not truly symmetrical and it runs a bit of an angle and I've heard people have put a hydrofoil and solved that problem.

So I think the bottom line for me is if your boats running fine there's no point. If you find there's a problem then maybe it's worth experimenting as a way to solve that problem. All right suns come out now and I can't be bothered changing the exposure so it's time to go. I hope this gives you an idea of how to install one of these and maybe what some of the benefits might be for you. I haven't noticed any huge improvement with this boat but then again the boat didn't have any problems to start with so maybe fuel mileage may vary. All right well, take care, I will see you next week.