Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

[kfa4303]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Good call yugom70. If your anti-vent plate really is that low, that's your problem. It should just barely break the surface when on plane as in the pic you provided. It just takes lots of trial and error to find the best combo of tilt trim and motor height, but once you figure it out you'll never have to fiddle with it again. From my own experience, raising my motor and redesigning the layout to better distribute weight, has made a huge difference in my boat's performance. Jackplates, trimtabs, tiller extenders and other non-mechanical aides are great boat mods that can make a world of difference and can often be DIY using common materials to save on costs (i.e. aluminum angle jackplates, PVC tiller extenders, trim tabs made from SS door hinges, etc...). Keep us posted on your results.

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Your really up against it with your weight.Picture a 9 ft dingy about 100 lbs with a 9.9 and one person it would really scoot but add two more adults and it will struggle.Your way beyond that.
In the old days we called the stick you put on top of the transom to hold the motor uo "rev sticks"
Your obviously handy you might make some "after planes"A wooden structure to extend the bottom beyond the transom
6 or 8 inches.It would add some planing surface where you need it most. these would be full width except for and area open for the motor.These aren't to handy for backing up. Perhaps you could fabricate large simple trim tabs that would be simpler than an after plane
yet could be adjusted slightly for best affect.

I was a some point going to try and make my own trim tabs, but think I will buy those made by Smart tabs, what I love about this idea is the hydraulic shocks at rest will push the tab down at a slight angle, then as you accelerate, the resistance in the water flow pushes the trim tab back for less water resistance. And if I need more weight on my shocks than standard small boat 20lbs say(which is probably obvious)lol, they will exchange for more resistance shocks. Too cool and for a little over a $100 seems good to me. I tried looking at shocks and doing it all myself and really no money savings and hard to figure out resistance etc. I think we are on the right path Steele, and friends! Thanks! I meant to say I need to mount a jack plate which I can fabricate once I dial in exactly how many inches to I need to raise up the outboard, jack plate and proper engine height for my boat, heavy my guess 40# trim tabs is I think where I am going to start for my next mods. When I get this thing dialed in I think alot of boat owners will be able to get something from this hopefully.

 

[steelespike]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

The automatic affect of the Smart tabs is nice but::
I was thinking that if you made your own very basic, 2 pieces of plywood each about 20" long by 6 or 8 inches wide
a couple of turn buckles each side some sort of hinge.(piano hinge)? Start with them parallel with the bottom like extending the bottom.
only increase the setting if indicated.

 

[Texasmark]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

We only know what we are fed. AV plate 6" in the water speaks volumes but you still have the 15 degree thing to consider. Maybe we might get this resolved after all.

Mark

 

[fishndirk]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

I'm going to help you out here yugom70...no offense to you but your trying to polish a turd. I had a 12 ft boat with a 9.8 2 stroke on it that would do about 15mph by myself. Total load of maybe 500lbs in that condition. You say your boat itself weighs 400lbs...think about that...even with the most efficent prop you can run on that motor with whatever amount of bells and whistles you want to put on the boat, there's just no way your going to brake 15mph with your setup. If you want some more long term advice, you'll be better off saving the cost of a new prop and any other bells and whistles your talking about and just saving to spend a few hundred on a 10 or 12 foot flatbottom al, which would run awesome with a 9.9hp. What you have is a nice, slow trolling motor blue gill pond fishing boat which I have to say by the pics if you built yourself I'm rather impressed. Every boat has its purpose, know yours...

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

We only know what we are fed. AV plate 6" in the water speaks volumes but you still have the 15 degree thing to consider. Maybe we might get this resolved after all.

Mark

AV plate, jack plate has not been done the 15% TILT has didn't help much, some but not much. Also I sure hope to GOD, I don't need a 20" Trim tab. I know I only have a 4x8 piece of plywood flat bottom boat, and its built like a tank, would rather putt putt around the lake than have that kind of trim tab hanging off the back of my boat. I'd have to hang red flags off of them driving down the road...lol. That would probably work great, but trying to figure out a different solution. Was initially going to do 1/4" aluminum homeade trim tabs with SS turnbuckles too, and may still, but really like the idea of #40 hydraulic shock trim tabs that have adjustments. Now next to make a jack plate which will be easy, and to see what that will do for me. Thanks all, getting the wheels turning on this solution is critical! I am going to try to make a video of wake before and after Jack plate install so you can see what I see.

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

I'm going to help you out here yugom70...no offense to you but your trying to polish a turd. I had a 12 ft boat with a 9.8 2 stroke on it that would do about 15mph by myself. Total load of maybe 500lbs in that condition. You say your boat itself weighs 400lbs...think about that...even with the most efficent prop you can run on that motor with whatever amount of bells and whistles you want to put on the boat, there's just no way your going to brake 15mph with your setup. If you want some more long term advice, you'll be better off saving the cost of a new prop and any other bells and whistles your talking about and just saving to spend a few hundred on a 10 or 12 foot flatbottom al, which would run awesome with a 9.9hp. What you have is a nice, slow trolling motor blue gill pond fishing boat which I have to say by the pics if you built yourself I'm rather impressed. Every boat has its purpose, know yours...

With all due respect you may be perfectly right, I am not trying to make it a speedboat by any means. I am just trying to get where I am going and learn some things along the way to be truthful. Yes I could buy a 12 foot aluminum john boat or whatever pretty cheap, but I like the challenge here of learning how boats and engineering works more than anything. Polished turd maybe, but what I have learned so far I would have never learned anywhere else. Then when I buy my jetsled everthing will be super easy, because I will understand how everything comes together. Call it school of hardknocks, not like working on Grandmas chevy, water is a much different animal. Cheers!
P.S. What I really should have called this was my M.A.D. boating science experiment.

 

[steelespike]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

I somehow missed your anti vent plate being so low. Getting it up where it belongs will help some,
even if its just to get the prop out of harms way from being so deep.

 

[fishndirk]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Most boats in this size range will plane somewhere between 11 and 16 mph depending on several factors. I've tested it on gps in several different jon boats. Judging by the fact that your boat itself weighs twice as much as other boats in that size, I'm guessing you would need to be on the upper ange of that just to get it on top of the water. The weight distribution of how much surface area you have sitting on the water is just asking a lot of that 9.9 to accomplish. If your boat weighed around 200lbs or less it would be a whole different story. You say your total load is somewhere around 800lbs. Most people pushing loads like that are running 15 to 25 hp motors and on boats that are 12 to 16 feet which have a lot more bottom surface area to push off the water and get on top of it than what you have. Bottom line here: too much weight in too small a boat with too little power. Without changing one of these variables drastically you are not going to be able to gain more than maybe a couple more mph

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Most boats in this size range will plane somewhere between 11 and 16 mph depending on several factors. I've tested it on gps in several different jon boats. Judging by the fact that your boat itself weighs twice as much as other boats in that size, I'm guessing you would need to be on the upper ange of that just to get it on top of the water. The weight distribution of how much surface area you have sitting on the water is just asking a lot of that 9.9 to accomplish. If your boat weighed around 200lbs or less it would be a whole different story. You say your total load is somewhere around 800lbs. Most people pushing loads like that are running 15 to 25 hp motors and on boats that are 12 to 16 feet which have a lot more bottom surface area to push off the water and get on top of it than what you have. Bottom line here: too much weight in too small a boat with too little power. Without changing one of these variables drastically you are not going to be able to gain more than maybe a couple more mph

Trust me I agree with you fully. I do have the Boyessen power reeds and 4 blade power prop on the 9.9. These mods alone make the motor a tractor. I seriously think its doable still though. It might not plane with 2 people and gear, but I think it will scoot enough not to be dangerous in a little chop and such. Will let you know more once I get get a little time and money together to continue on this "boating science" experiement. This will work, watch. The other thing I can easily do hmm hmm... for around another $200 bucks, is a Merc 15 hp Carb. I will be doing this, along with the other things, and it will not be for lack of power that this boat is not planing. Damnit I will not stop till I have tried every trick and or mod to make this thing work! Stubborn sorry .

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Ok if the weather holds out will be taking my boat out soon after I make a makeshift jackplate. I will take out everything but myself, gas can, motor, a little fishing gear etc. which should bring it in around 600 lbs ish. If I can't plane, I'm selling it! My eyes are now on a Boston Whaler yacht tender 11ft. LOL sheesh!

 

[steelespike]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Just thought I'd mention there is a video on you tube of about a 10 ft jon boat with a 2 hp evinrude obviously very light
and a light person running it.It actually planes. just an indication of how well a boat can do when the foot print and
boat weight matches the load and power of the motor. just search 2 hp jon boat.

 

[fishndirk]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

An 11 foot Whaler and a 9.9 would do very nice. With all the money and effort you have spent on this rig so far you could have already bought something like that. If you say you want to experience how boats work than trust me, as soon as that 9.9 gets that whaler up on plane you will understand, and it won't be long after that till your wanting to see what more you can get.

 

[yugom70]

Re: Prop Help! for Heavy 10ft Jonboat with 9.9 hp 2 stroke Merc

Yeah thanks for reminding me on how much I have spent...lol Yeah now to find a whaler!