I haven't done it, but you're right about the tunnels. They rob a good amount of speed depending on the design - the tunnel sucks the boat down the faster you go. If you're seeing 32 now, you'd probably gain anywhere from 4-8 MPH.

That's why the shallow running cat designs are catching on so well. Best of both worlds with speed and shallow running.

 

I have a 15' 48" mod-v with a 50 johnson side console and I get 34mph by myself and 32 with 2 other people in it.

 

look into venting the tunnel hull.

 

x2

Venting should give you back all of your speed, and let you keep your shallow-running ability.

To the OP, you really should have a good tach on that boat so you know your rpms. Then you can fine-tune the prop to get best performance. IMHO, either Baumann or Powertech make good tunnel props.

Check out the Boats, Blinds & Gadgets forum over at refugeforums.com - they have a lot of info on running tunnel boats.

 

Alot of guys add some mods to the motor like putting 60 hp carbs. might help get you to 40 mph.

 

Sounds like you are looking at putting a lot of money into a rig that MIGHT get you 5-6 mph faster. Maybe??? with all the work and rigging.

Sounds like the prop is working well but cheapest is to get with Louie Baumann and get his prop test on your prop to see it it can be reworked to get a few extra mph or better jump.

Louie had posted his test for boaters to go out on their on and do the testing at different jp settings, and tilt setting in one of the old Texas SW fishing mag archrive articles. Check it out. 4 -5 years worth of old mags to read for free on a rainy day.

I would save the money and use it for more fishing trips and gear unless you want to just spend the time and money for the fun of rigging which I have been known to do too.

 

Sounds like you are looking at putting a lot of money into a rig that MIGHT get you 5-6 mph faster. Maybe??? with all the work and rigging.

Sounds like the prop is working well but cheapest is to get with Louie Baumann and get his prop test on your prop to see it it can be reworked to get a few extra mph or better jump.

Louie had posted his test for boaters to go out on their on and do the testing at different jp settings, and tilt setting in one of the old Texas SW fishing mag archrive articles. Check it out. 4 -5 years worth of old mags to read for free on a rainy day.

I would save the money and use it for more fishing trips and gear unless you want to just spend the time and money for the fun of rigging which I have been known to do too.

Well said, a fact that I am well aware of and brother you are not alone spending time and money for the fun of rigging!

R

 

leave it and just leave earlier, you are asking for trouble

wear your kill switch

 

There was a good thread on hear by a fella with the same boat but 16' with at 115 2s! and all he got was 32mph. That is before and after venting the tunnel. Maybe he will chime in and correct me if I am wrong. I was wondering if I closed in the tunnel would I get 40 mph, no other mods. I cannot find ANYONE with a 48" bottom jon boat that is going faster than 32-34 so it maybe a limitation of the design.

Has anyone else put a tach on a manual start, no battery 4s tiller motor?

R

 

Thanks for the info. It maybe as I suspected, unreasonable to get one to 40 mph with 40hp.

R

 

40

Thanks for the info. It maybe as I suspected, unreasonable to get one to 40 mph with 40hp.

R

X-2 ain't gona happen tunnel or no tunnel.....CVA34

 

Id rather have the tunnel. But I fish shallow.

 

I run a 16' Excel F4 with a Yamaha 2s 50 and we see 37 light. I duck hunt with a guy that has the same boat with a 90 on it and he sees 52 but he has to keep 200 lbs. of rice on the bow due to bow rise while getting on plane. Most boats are not built for speeds higher than 30 mph and the limitations of the hull won't let you get faster no matter how much HP you put on the back. Venting the tunnel should help but all the work of closing in the tunnel may not give you gains you are looking for.

 

Thanks for the info. 50-90hp (+200 lbs of duck food) gets you from 37-52 mph is pretty telling. Can you be cited for baiting with 200 lbs of rice in the front of the boat on a duck hunting trip.

Is closing the tunnel harder than venting it. I have no trouble welding a couple of 1/8" AL plates to close in a tunnel, but cutting a hole in the bottom of the boat I'd have to think twice about. Do you know anyone who has run a boat (regardless of size and speed) with a tunnel, keep good speed records, then vented the tunnel and had an increase in speed. I have only seen examples where venting reduced draft of hull under speed. What I mean is they could run shallower with the vented hull because it was not sucked down into the water.

What methods of venting have you seen?

R

 

I HAVE A 18-70 W 115 2S AND ONLY GET 44 AT BEST. YOU WILL NOT HIT 40 W/ 40 NO MATTER WHAT YOU DO. THE FASTEST WELDCRAFT I HAVE EVER SEEN WAS A 20-70 WITH 150HO ETEC. 52MPH. THEY START ACTING REALLY FUNNY AFTER 45. NOT SAFE. KEEP YOUR BOAT THE WAY IT IS. NO MATTER WHAT YOU DO, YOU WILL NOT BE SATISFIED.

 

20-70 at 52 with a 150 is good info. Are there are ALOT of 20' fiberglass bay boats that will hit 52 with the same HP?

 

Keith is right, the boat is a 14' Excel F4 with a yammi 90.

 

27contender

I had just picked my stainless prop up from baumanns and 34 was my new top speed. Before that the best I could get out of it was 29mph. He increased my pitch from 13 to 14 and put some cup in it and it made a world of difference. Take your prop over there and tell him your setup and see what he thinks. Their very friendly and will help you out, they don't mind talking with you at all. Thats your best bet for increasing your mph for the least amount of money or work.

Turn around time was quick, I dropped it off midday on a Tuesday and picked it up Thursday morning. Best money I've spent on my boat as of yet.

 

27contender

I had just picked my stainless prop up from baumanns and 34 was my new top speed. Before that the best I could get out of it was 29mph. He increased my pitch from 13 to 14 and put some cup in it and it made a world of difference. Take your prop over there and tell him your setup and see what he thinks. Their very friendly and will help you out, they don't mind talking with you at all. Thats your best bet for increasing your mph for the least amount of money or work.

Turn around time was quick, I dropped it off midday on a Tuesday and picked it up Thursday morning. Best money I've spent on my boat as of yet.

Not sure what prop work will do with this set up. I do not have a tach as it is an all manual set up. Not sure if a tach is possible. I would not know how to advise Louie. I love the BLACK MAGIC of doing prop work too. I have 3 sets for the other boat and I think I have found the HOLLY GRAIL of props! I just have to spend another 100 hours figuring out what to have Louie change. Im sure Ill find something.

Thanks

R

 

14 x 42 Southfork, vented tunnel, sponsons, and a 40 Nissan and get 35 light. If I close the tunnel vent I lose 2-3 mph. If you don't have a vented tunnel, I'd definitely do that as its relatively easy and gives you both shallow water and speed performance. Also check your sponsons as they may be dragging - mine are but I've not fixed them as I'd probably get more speed but would also likely porpoise more. If you vent the tunnel you won't lose speed from the foil as it will be out of the water while running.

 

Sponsons come up just a tad form the bottom of the hull. Not sure how to vent the tunnel on my boat. Id have to post pictures to show you.

R

 

yes

there are some fiberglass boats that will do 52 w/ 150. the thing with aluminum boats is that you can only go wide open in optimum conditions. which in south texas is not very often. aluminum boats just beat you up at high speeds with any chop.

 

Might be right on no 40 with 40.

 

pm sent

 

Ask Louie for his opinion. He is "the expert" to see if he can help you improve what you have. He has seen about everything with all the years they have done props

 

You can do 40 with a 40. I have a 14'x48" with 40hp suzuki 2-stroke and it will do right about 38mph. It will also do 36 with 3 people in it. I have no tunnel. Also helps that I have power trim. I'd hit over 40 if I had the prop worked on. It's a 13 pitch and needs to be about a 15 pitch, also got some dings in it, think one blade is bent.

If you don't care so much about quick takeoff or slow speed on plane, play with trimming the motor up. You should have some sort of stops you can adjust, or get some motor wedges. I can hardly hit 30mph trimmed all the way down.

Oh, you don't get steering control at much over 30mph.

 

You can do 40 with a 40. I have a 14'x48" with 40hp suzuki 2-stroke and it will do right about 38mph. It will also do 36 with 3 people in it. I have no tunnel. Also helps that I have power trim. I'd hit over 40 if I had the prop worked on. It's a 13 pitch and needs to be about a 15 pitch, also got some dings in it, think one blade is bent.

If you don't care so much about quick takeoff or slow speed on plane, play with trimming the motor up. You should have some sort of stops you can adjust, or get some motor wedges. I can hardly hit 30mph trimmed all the way down.

Oh, you don't get steering control at much over 30mph.

I have a different lower unit ratio I think 2:1 I run a 15 solis 3X 10.5. I am getting quite a bit of slip 20%+ but might be due to tunnel or lack of trim. I get about 29 with 3. I still have not decided to close it in, but Id like 38 light and 36 with some people in exchange to 5" more water.

R

 

I ave 17 ft express boats with 90s that will hit 50mph. it all comes down to hull design. We also have 15ft flat bottoms in south east texas with 40 mercs that will hit 60 mph

 

Wow, what do the 15ft FB with 40's look like.

R

 

I'm with dixie on this, I own a 25 yamaha 3cyl on a 15 42 southfork with vented tunnel. It will do 34 when the water falls out of the tunnel due to venting. I got this setup for shallow fishing and duckhunting at Keith lake so I plugged the tunnel(didn't care about speed). The bad thing about vented tunnels is if you set your motor heighth at the highest possible location for gettin up shallow is if you catch air your water falls out of your tunnel and your water pick up either is out of the water or isn't gettin enough water then you burn your motor up. I now can only do 28 29, but can get up in 4 inches of water and probably run in 2 if not for a long distance.

And the boat in my avatar is the 15 42 with a 60 hp Yamaha that I bought to play with. It made 55mph and I still had throttle left. I also still have a long time left to live so I took it off. It had a 19p prop on it at the time. I also had a 15p for hole shot. Oh and at the start of that trial the water dropped out of the tunnel so the boat wasn't sucked to the water.

 

Electric tilt and trim would help. I do not have it and want to stay light so I wont add it. I have hunter Keith Lake in the past. BOat ran the ditch and ponds pretty well. I do not get up in 4" of water, it will run that shallow.

Is the avatar boat a tunnel or is the jack plate there to accommodate the longer motor?

 

Just put a bigger motor on it, a longer tiller handle and go as fast as you want. Put a 200 on a 16' and it will haul assss.

Get er dun!

Oh and add an extra bracer bar or 5 to the transom

 

16' Alumacraft with center console and a 48SPL will run 34mph with me and one ove my sons.Not sure I would want it to go faster,ok maybe a little.

 

I've got a Monarc 15 ft with a 5 degree V bottom ,with a Johnson 40 that will come really close..up for sale if you are interested,send me a PM....

 

Here's something to consider. I have seen this boat run and it's a bad fast 1648 Weldbuilt with a 50 Tohotty. Enjoy!

This boat will run 62MPH you can check out his other videos on youtube. Pretty dang cool.