Help me make my Glen L Stiletto Wooden boat FASTER!! (Advice needed)

Hello, I have a 16 foot Glen L Stiletto Boat. It is a completely wooden home built boat. I wish I could claim that I made it... but I didn't! I have used it for a few years at 5600' elevation. At this elevation I had to detune the boat to run OK at high elevation. At this elevation, the boat would run an honest 45 MPH. Now I am operating the boat closer to 1000' elevation, I retuned to stock and the boat runs an honest 55 MPH. Now I have caught the speed bug!!The boat weighs a little over 900 pounds with motor. I have a 1997 Evinrude 115 60 degree outboard with a 19 pitch Stiletto prop.The motor is set to the lowest height setting. I just purchased a water pressure gage. Next I am going to start raising the motor.My next move will be a jackplate and then.....????
For now, here are some pictures of the boat. More questions are coming.


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Here is a picture the previous owner gave me. As you can see, not much bow lift. You can see he is trimmed out... would raising the engine help here? Remember, it is at the lowest setting.

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Pictures of the structure..

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Now here is one problem I need your opinion on. The previous owner installed a fin (skeg) in the middle of the boat to help with stability... This does help the handling, but I am focused on going faster. What is your opinion on this fin?

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The previous owner installed these adjustable trim tabs.. Do these help or hurt higher speed performance?

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Side profile view of boat....

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Raising the motor will reduce bow lift. Adding setback will help carry the bow. I wonder if the trim tabs were added to address a porpoising problem. They might be keeping the bow low. The fin will greatly improve cornering but will cost speed.
Pretty boat.

I see your point.. With this boat only being 16 foot long, I don't think I need to set back the engine.

Next time I go to the lake I can remove the trim tabs and experiment. I will also raise the engine because I feel the engine sits way too low in the water.

I want to systematically try one thing and then run it with GPS to keep track of what I am doing.

Is it OK to spin this Evinrude to 6000 RPM?

Always liked the Glen L boats and the Stiletto has always been one of my favorites. Looks like it was a very nice build.

Where is the fuel tank? Sometimes they were put in the bow which could make it bow heavy.
The trim tabs look like they are flush to the bottem of the boat. I was always told this was a no no as it causes more drag. Should be minimum of 1/4" above the bottom.
Your 55 mph speed is quite respectable for that package but it does look like it's running pretty wet and should have room for improvement.

I wouldn't run it without the skeg as it won't turn but skid. Have you put a straight edge on the bottom to be sure there is no hook?

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Originally Posted by 80's old school

I will also raise the engine because I feel the engine sits way too low in the water.

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What height (above bottom surface) is the centerline of motor torpedo currently (at 55mph)?

Nice boat. Since it is a flat bottom, you will not get much bow lift and you don't want much bow lift. Raising the motor will reduce drag, increase RPM and the boat will improve top end, slightly. You should be running only a small amount of positive trim.

On a trailer, measure the prop shaft to the bottom of the boat, it's easier to measure the anti-ventilation plate but most use the prop shaft. Expect about 100 RPM per inch more as you raise it. With this set up, just do a moderate increase. You can probably squeeze a couple MPH out of it. That is a nice setup. The trim tabs are probably there, like the others mentioned for porpoising, that flat hull should plane no problem.

The mid 50's speed range is good for that hull.

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Originally Posted by Jimboat

What height (above bottom surface) is the centerline of motor torpedo currently (at 55mph)?

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Are you referring to the engine being level and then the difference between the propshaft centerline and the bottom of the boat?I don't have the boat here with me now, but just guessing / estimating the centerline of the propshaft is about 5-6 inches below the bottom of the boat with the engine being level.My boat is at our Lake house. I can go there tomorrow and check measurements. Please describe exactly what I need to measure and I will report back. Thanks!

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Originally Posted by Onetime

Always liked the Glen L boats and the Stiletto has always been one of my favorites. Looks like it was a very nice build.

Where is the fuel tank? Sometimes they were put in the bow which could make it bow heavy.
The trim tabs look like they are flush to the bottem of the boat. I was always told this was a no no as it causes more drag. Should be minimum of 1/4" above the bottom.
Your 55 mph speed is quite respectable for that package but it does look like it's running pretty wet and should have room for improvement.

I wouldn't run it without the skeg as it won't turn but skid. Have you put a straight edge on the bottom to be sure there is no hook?

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Thank you for the compliment! The guy who built it did an outstanding job!

The fuel tank is in the center of the boat. The pictures describe it best. I think he put the tank in a reasonable location.

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The trim plates are flush to possibly 1/8 inch above the bottom of the boat. I can measure tomorrow to be exact. Luckily they are easy to remove to test and easily repositioned if needed.

As for the fin / skeg, I would like to get more of the boat out of the water. If more boat is "not wet", then the fin will be less an issue. I could also "profile" the fin shorter if this would help with top end performance.

I will check tomorrow to see if there is any hook. At first glance I would say no, but a straight edge will tell the story.

Thanks for the info!!

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Originally Posted by blacktruck

Nice boat. Since it is a flat bottom, you will not get much bow lift and you don't want much bow lift. Raising the motor will reduce drag, increase RPM and the boat will improve top end, slightly. You should be running only a small amount of positive trim.

On a trailer, measure the prop shaft to the bottom of the boat, it's easier to measure the anti-ventilation plate but most use the prop shaft. Expect about 100 RPM per inch more as you raise it. With this set up, just do a moderate increase. You can probably squeeze a couple MPH out of it. That is a nice setup. The trim tabs are probably there, like the others mentioned for porpoising, that flat hull should plane no problem.

The mid 50's speed range is good for that hull.

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Thanks! I will measure as you mentioned tomorrow.

I was wanting a goal of mid 60's with a dream of close to 70... Is this impossible with this type of hull? Or just impossible with that motor?

Future Mods I was thinking about were as follows:

Jack Plate
Prop Change if needed
Trim Tab move (if needed)
Milled Head (higher compression=more power)
Boyeson Reeds

I know the fastest way to have a faster boat is to buy a faster boat.... I just like the classic looks of this boat and love the compliments every time it is on the water. I want to also impress with its performance.

Let me know if these goals are unrealistic... I could always looks for a larger engine, but it would be nice to make do with what I have.

Great looking Boat.....I wish I had the skills to build something like that. That is a pretty shallow (flat bottom) and I don't see that 115 getting much faster. Without lifting strakes the hull isn't going to come out of the water like a Deep Vee. So the hull will always have a lot of water surface area contact limiting the speed.

55 MPH is very respectable for an all wooden boat with a 115 HP motor.

I have the opposite problem with a 16 ft Deep Vee (no Pad) and a 150 Optimax on the back......I am told the boat should do 80 but will chine walk at 55-60 and no way to get rid of that without the pad.

Again, awesome little boat.

Karsten

Set up is the first thing I would improve for more speed as said before. I would also check to see if that is the largest hp engine built on that platform. I have seen carb and timing changes add some good hp to the proper motors. I would check this before making a prop change. Gary

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Originally Posted by Karsten

Great looking Boat.....I wish I had the skills to build something like that. That is a pretty shallow (flat bottom) and I don't see that 115 getting much faster. Without lifting strakes the hull isn't going to come out of the water like a Deep Vee. So the hull will always have a lot of water surface area contact limiting the speed.

55 MPH is very respectable for an all wooden boat with a 115 HP motor.

I have the opposite problem with a 16 ft Deep Vee (no Pad) and a 150 Optimax on the back......I am told the boat should do 80 but will chine walk at 55-60 and no way to get rid of that without the pad.

Again, awesome little boat.

Karsten

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Well luckily I don't have any problems with Chine walk! This boat exhibits Zero chine walk all the way to 55 MPH.

The boat gets faster and faster the more you trim, but the porposing gets to be too much. I can run the speed up to 55 and it is bouncing... Trim down slightly and she runs 50 mph as smooth as glass.

Since this is a wood boat, could some form of pad be built to the bottom and faired in? I know this is not an easy proposition, but I am never one to take the easy route always!!!

I think just raising the motor to optimum height, which will probably be just 2 or 3 inches hire than the plate lined up with the bottom will make it a little faster and improve handling. When a lower unit is too low it drags through the water and can cause handling issues.

Personally, I think you're running that boat in the sweet spot. You can mod the engine, but the hull is limited and it would take too much modding to get it close to 70's. The hull is not really designed for those speeds. I'd say play with the engine height, props etc. Have a safe handling, respectable performance boat that's economical. If you want to go 70 plus someday, invest in a hull designed for that kind of performance. Just my 2 cents.

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Originally Posted by 80's old school

Thanks! I will measure as you mentioned tomorrow.

I was wanting a goal of mid 60's with a dream of close to 70... Is this impossible with this type of hull? Or just impossible with that motor?

Future Mods I was thinking about were as follows:

Jack Plate
Prop Change if needed
Trim Tab move (if needed)
Milled Head (higher compression=more power)
Boyeson Reeds

I know the fastest way to have a faster boat is to buy a faster boat.... I just like the classic looks of this boat and love the compliments every time it is on the water. I want to also impress with its performance.

Let me know if these goals are unrealistic... I could always looks for a larger engine, but it would be nice to make do with what I have.

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Originally Posted by blacktruck

I think just raising the motor to optimum height, which will probably be just 2 or 3 inches hire than the plate lined up with the bottom will make it a little faster and improve handling. When a lower unit is too low it drags through the water and can cause handling issues.

Personally, I think you're running that boat in the sweet spot. You can mod the engine, but the hull is limited and it would take too much modding to get it close to 70's. The hull is not really designed for those speeds. I'd say play with the engine height, props etc. Have a safe handling, respectable performance boat that's economical. If you want to go 70 plus someday, invest in a hull designed for that kind of performance. Just my 2 cents.

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I will start with this first. I need to install my water pressure gage first. Then I will raise the motor incrementally. Since it is in the lowest position now... I have 3 more positions to raise.

Since I don't have a jack plate, I will take my engine hoist to the lake. I can make adjustments...run the boat and evaluate and then make adjustments again..


I appreciate everyone's advice. I just want to tune to the sweet spot to make this rig run the best she can... maybe 60 MPH is a more realistic expectation / goal!! :)

Ya, you got it. This will help with porpoising too, with the motor raised, you can run it flatter while reducing drag. You really don't need much trim on a flat hull like that. Good luck.

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Originally Posted by 80's old school

I will start with this first. I need to install my water pressure gage first. Then I will raise the motor incrementally. Since it is in the lowest position now... I have 3 more positions to raise.

Since I don't have a jack plate, I will take my engine hoist to the lake. I can make adjustments...run the boat and evaluate and then make adjustments again..


I appreciate everyone's advice. I just want to tune to the sweet spot to make this rig run the best she can... maybe 60 MPH is a more realistic expectation / goal!! :)

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I would say to get 60 mph out of that hull with 115 hp is doing very well. Gary

We built one of those in the early 70s. Without a keel or skeg the boat was very sktchy when turning. It also help stability when operating at wot. I recommend keel/pad ....the skeg in the midship could cause the boat to hook when turned real sharp.

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Originally Posted by 80's old school

...guessing / estimating the centerline of the propshaft is about 5-6 inches below the bottom of the boat with the engine being level.

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Raising the motor will definitely give you more speed, as your current setting stated seems pretty low (so, a lot of unnecessary drag). You should get a several more mph by raising height. You should get be getting good water pressure even raising your motor since you're well buried in the water now, but a water pressure gage is always the best insurance.

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Originally Posted by 80's old school

The boat gets faster and faster the more you trim, but the porposing gets to be too much.

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This hull is susceptible to porpoising, probably see it starting at ~40mph right through to 60mph. Flat bottom is more susceptible to onset of porpoising. Changing engine height may also improve porpoising issue. [see article on Porpoising]

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Originally Posted by 80's old school

...could some form of pad be built to the bottom and faired in?

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Flat bottom won't benefit from a pad, since flat running surface is already very efficient.

In addition to all the good advice above.....possibly just raising the engine and switching to a big ear chopper prop will help. Choppers will add some bow lift to this boat and throw more water than an omc thru hub

Jimboat, thanks for the input. The more I read the more I learn. I will be heading up to the Lake House today to get actual numbers on the requested motor height, checking for hook in bottom of boat, etc.

Thanks to everyone contributing. This is a very engaging forum... the more I read, the more I learn.

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Originally Posted by Bodhi

In addition to all the good advice above.....possibly just raising the engine and switching to a big ear chopper prop will help. Choppers will add some bow lift to this boat and throw more water than an omc thru hub

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I was wondering about Chopper Props.. If advantages are faster speed...what are the disadvantages?

Does anyone know what the rev limiter is on my 1997 Evinrude 115 60 degree Eagle motor?

Also, is the rev limiter a hard rev limiter where you know it hits because it abruptly shuts down speed, or is it a soft limiter where it simply drops some cylinders where it smoothly settles at the rev limit?

Also for short bursts, what is the max RPM this motor is good for? I premix with Evinrude XD100, so I feel I am putting my "best foot forward" with lubrication.

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Originally Posted by 80's old school

I was wondering about Chopper Props.. If advantages are faster speed...what are the disadvantages?

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No disadvantages really, they are specific for they're purpose. ..bow lift. There are many styles to the chopper , one being a small ear which will spin higher rpm with a bit less bow lift. I personally like big ear choppers for flying the bow high. Cleavers on the other hand will give stern lift . But anyone will tell you, you'll go through a few props before you find that "sweet" one. Took me 4 props to find my cleaver that flys me just right

Measured a few things today as requested.

1. Propshaft centerline is 8.75" below bottom of boat.
2. Cavitation plate is 1" below bottom of boat.
3. Bottom measures flat. No hook noted. No flaws or issues noted on hull.
4. Trim Tabs are mounted flush to bottom of boat.

Looks like a jackplate plate will be needed. I only can move up the engine another 2". That will still put me at 6.75" prop centerline below bottom of boat.

Based on your measurements, I'd say you can move the motor up quite a bit - assuming you still have adequate water pressure. Moving the motor back with a Jack Plate will help even more since you'll gain leverage to lift the bow. With a stock 115 on her, I'd be quite happy with around 60 MPH.

As for the Trim Tabs, as others have said, they're probably there to address the porpoise issue you're still seeing some of. Moving them up so that they're not parallel with the bottom will reduce drag. Generally speaking, you want to be up the transom at least 1/4".

One final thought. Moving all of the stuff around on that beautiful transom will involve removing and re-installing fasteners. Make sure you carefully / fully re-seal the holes when you put anything back in place. I'd hate to see you ruin that beautiful boat by getting water into the transom structure and rotting it out.

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Originally Posted by 80's old school

Measured a few things today as requested.
1. Propshaft centerline is 8.75" below bottom of boat. 2. Cavitation plate is 1" below bottom of boat. 3. Bottom measures flat. No hook noted. No flaws or issues noted on hull. 4. Trim Tabs are mounted flush to bottom of boat. Looks like a jackplate plate will be needed. I only can move up the engine another 2". That will still put me at 6.75" prop centerline below bottom of boat.

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At the height you've measured, the height of your motor is certainly affecting your top speed, acceleration and handling. There is too much lower unit in the water, creating a lot of drag. The important measure is the location of the lower unit 'torpedo' (prop shaft), not necessarily where the cavitation plate is located, but if your lower unit height is sufficiently low that the cavitation plate is actually wetted, then this is creating a huge amount of unnecessary drag. Raising your engine will help your top speed significantly and will also reduce the 'bow-down' moment currently causing significant hull bottom wetting (and drag). The location of your Dynamic CG will also be altered somewhat by raising your engine, which will change the susceptibility to porpoising. If your engine is a long shaft model, this could be the height issue, short shaft engine is intended for this boat. You might be able to simply build up your transom if you don't wish to go to the expense of a jack plate. You can also expect that your prop selection can change somewhat with the change in engine height.

Here are some pictures I took today.. They show how low the motor really is and how the Trim Tabs are flush to the bottom of the boat.

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Work is needed!!!

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Originally Posted by TooStroked

Based on your measurements, I'd say you can move the motor up quite a bit - assuming you still have adequate water pressure. Moving the motor back with a Jack Plate will help even more since you'll gain leverage to lift the bow. With a stock 115 on her, I'd be quite happy with around 60 MPH.

As for the Trim Tabs, as others have said, they're probably there to address the porpoise issue you're still seeing some of. Moving them up so that they're not parallel with the bottom will reduce drag. Generally speaking, you want to be up the transom at least 1/4".

One final thought. Moving all of the stuff around on that beautiful transom will involve removing and re-installing fasteners. Make sure you carefully / fully re-seal the holes when you put anything back in place. I'd hate to see you ruin that beautiful boat by getting water into the transom structure and rotting it out.

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Thank you for the words of advice!! I will make sure to seal everything up after making modifications... I want her to be around a long time!

From the pics you posted, I'd bring the motor up 2inches to start.....it's sitting way too low.
.....and just to correct terminology for you, the plate above the prop is not a cavitation plate as most commonly call it, it is an anti-ventilation plate. Just in case you deal with a marina in the future that refers to its proper name

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Originally Posted by Bodhi

From the pics you posted, I'd bring the motor up 2inches to start.....it's sitting way too low.
.....and just to correct terminology for you, the plate above the prop is not a cavitation plate as most commonly call it, it is an anti-ventilation plate. Just in case you deal with a marina in the future that refers to its proper name

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Thanks for clarifying that. I will bring the motor up the 2 inches that I can and see what that brings. I will bring the boat down next week and start installing the water pressure gage as well as raise the engine as much as I can (2 inches).

How 'bout these for a Jack Plate? I think these should do the trick!

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Originally Posted by 80's old school

Thanks for clarifying that. I will bring the motor up the 2 inches that I can and see what that brings. I will bring the boat down next week and start installing the water pressure gage as well as raise the engine as much as I can (2 inches).

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After you raise the motor and feel the benefits of less drag, you'll be able to go higher with a jackplate and a low water pickup. Bob's machine shop down here in fl makes a great nosecone and jackplates. Then all that's left is to find the "perfect" prop....

Ok so I'm reading all this advice and most all of it is good.
I've built these Glen L boats and to me the transom was kind of a weak link. These boats don't have the strength in the transom area as a fiberglass boat does.
JMO but I wouldn't even consider putting a jack plate on it. Also it's a 16' boat! I don't think it needs any increased set back without adversely affecting the cg.
Again, just my opinion

You can definitely raise the engine but I would keep it bolted to the transom. Just raising it is going to put enough increased stresses on the transom.

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Originally Posted by Onetime

Ok so I'm reading all this advice and most all of it is good.
I've built these Glen L boats and to me the transom was kind of a week link. These boats don't have the strength in the transom area as a fiberglass boat does.
JMO but I wouldn't even consider putting a jack plate on it. Also it's a 16' boat! I don't think it needs any increased set back without adversely affecting the cg.
Again, just my opinion

You can definitely raise the engine but I would keep it bolted to the transom. Just raising it is going to put enough increased stresses on the transom.

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Agree re jack plate/setback. Transom rebuild (raising) is structurally best option.

I would bet money that if your fuel tank was empty and you had a small 6 gallon portable fuel tank in the back you would pick up speed. Usually a mid tank such as yours will cost you speed compared to a rear mounted tank in flat bottom boats. Might be worth a try.

Good luck, Carter

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Originally Posted by Carter Powell

I would bet money that if your fuel tank was empty and you had a small 6 gallon portable fuel tank in the back you would pick up speed. Usually a mid tank such as yours will cost you speed compared to a rear mounted tank in flat bottom boats. Might be worth a try.

Good luck, Carter

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I had wondered about the center mounted tank in this boat and it riding so wet. I have a 12 gallon tank in the back of my 16ft and keep going back and forth about a 13 gallon bow tank under the deck.

http://imagizer.imageshack.us/v2/640.../dscn06717.jpg

Now with the Optmax I also have the 3 gallon oil tank back there as well as 140 extra pounds of motor over the 125 Evinrude.

Karsten

I would venture to say that the tank is mounted somewhere around cg and is not adversely affecting performance.
Do one thing at a time. Raise the engine one hole, which should be 3/4" if it's a standard BIA pattern, and test. First thing make sure you have good water pressure and try it. Then go the next hole and test, finally the last hole as long as water pressure, handling and speed are good.
You haven't mentioned what prop your running. Some stock type props won't surface well and might need to be changed out to see results. Choppers are great for performance but depending on boat use it might not be suited for the use. I.e. Wake boarding, tubing, etc.