Jack plate confusion

[jimbob669]

I recently bought a 16 foot Aluma Weld jon. It came with a 9.9 but with a manual jack plate. The boat lacks speed and rides very high in the front. It's rides so high that it's hard to see over the front. The guy I bought it from said the jack plate probably needed to be adjusted but he never messed with it. Does anyone have any idea how and where it should be set? I haven't seen many 9.9's with jack plates. Is it possible that my problems are due to having a jack plate on such a small motor? I would love for it to level off when running wide open and I wouldn't mind gaining a few more miles per hour. Any ideas out there?

 

[Lrider]

Re: Jack plate confusion

Boating 101 - how is your motor tilted - further out nose up further in (towards the transom nose down

I think

 

[bob johnson]

Re: Jack plate confusion

I recently bought a 16 foot Aluma Weld jon. It came with a 9.9 but with a manual jack plate. The boat lacks speed and rides very high in the front. It's rides so high that it's hard to see over the front. The guy I bought it from said the jack plate probably needed to be adjusted but he never messed with it. Does anyone have any idea how and where it should be set? I haven't seen many 9.9's with jack plates. Is it possible that my problems are due to having a jack plate on such a small motor? I would love for it to level off when running wide open and I wouldn't mind gaining a few more miles per hour. Any ideas out there?

Id guess your problem MOSTLY comes from having too big-and or heavy a boat for a 9.9 hp!!!

you probably cant get on plane......

the jack plate if it has any depth ( setback) is probably making it worse..
the jack plate might help if you could get on plane...

try adding weight up front or moving as much weight forward as possble.

even use a long tiller extension and get up from and drive....just to see if that gets you up on plane

bob

 

[jimbob669]

Re: Jack plate confusion

The 9.9 has a kit, not that it will really help all that much. Do you think the boat would run more level if I did away with the jack plate completely? Is it common to see a jack plate on a 9.9 or 18? I should also mention that the boat is equipped with an 80 lb thrust 24 volt trolling motor, so there are two batteries in the back which won't help my high front end issue. The front deck is hugh though and is build similar to floor joists with 2x4's, so I know there is plenty of weight in the front end. I have to stick with the small motor because most of the lakes around here have a ten horse limit.

 

[jimbob669]

Re: Jack plate confusion

The jack plate is 5 inch. I forgot to mention that.

 

[5150abf]

Re: Jack plate confusion

First make sure the pin on the engine is on the last hole closest to the boat, the farther you tip the engine up the more bow lift it will give you.

How does the boat sit at rest, if the transom is alot deeper than the bow you need to get some weight up front, starting with the batteries and if that doesn't do it then move the gas also.

A 9.9 on a 16 is asking alot of that motor and I don't think it will plane the boat so you are going to have to level the boat with weight transfer.

 

[bob johnson]

Re: Jack plate confusion

get a 15 hp and put a 9.9 cover on it...by eye you cannot tell them apart even with the cover off...

move the batteries up front!!! all it will cost you is the cost of cables...

get rid of the 2x4 constructed eck and make it out of aluminum...

you got a 16 ft boat and you have a 2x4 constructed deck up front????

and then you are trying to push it with a 9.9!!! thats the jist of your issue..

Id also make sure the pin is in the hole as close to the boat as possible and that the motor goes down against it!!

can you put the gas can up front????

is there foam in the boat???

it may be water logged and holding a hundred or more lbs of water

good luck

bob

 

[roscoe]

Re: Jack plate confusion

Boat to big and heavy.
Too much stuff in the boat.
Too small of a motor.
Jack plate.


"The 9.9 has a kit, "
Yeah, a kit that makes it run too rich and robs it of power.

There is no "kit" to turn a 9.9 into a 15. Only backyard tinkerers that screw up efficient running motors.

 

[bob johnson]

Re: Jack plate confusion

Boat to big and heavy.
Too much stuff in the boat.
Too small of a motor.
Jack plate.


"The 9.9 has a kit, "
Yeah, a kit that makes it run too rich and robs it of power.

There is no "kit" to turn a 9.9 into a 15. Only backyard tinkerers that screw up efficient running motors.

what about installing a 15 hp carb from the same year??

its not a KIT...

would that make a 9.9 a 15 hp?

talking to my mechanic about finding a short shaft drive shaft fior my 15, we talked about 9.9's and 15 hp..

he said that the 9.9 made about 11 or 12 hp and the 15 made about 13 hp...


he mentioned the same thing last year when i was workign on the 70 hp...said it made maybe 62 hp while the 55 hp made about 57 hp...

they were basically the same motor with different carbs...but the hp claims were stretched both ways to seperate them....dont know if its true...

but he is as much an old codger as they ever made!! ha ha

bob

 

[roscoe]

Re: Jack plate confusion

Use the search function to learn more, but your mechanic is misinformed.

Yes the carb may be the only external part that is different, but internal porting and exhaust baffling are different. The head and/or piston head may be different, as well as the intake, reeds, timing and max rpm.

This myth has been out there for 40 years.
If it was true and that easy, no one would ever buy a 15.
Or a 50 or 60 if they could just use a 40.
Or a 115 when they could buy a 90.

It is true that there is latitude in the rating of outboards to allow for part production variances, BUT... they have to be within 10% of the stated hp, and the last I read, the average of the motors coming off the production line has to be within 7% of the stated hp.

And if this is an older model, it was rated at the powerhead. After 1988+/-, they were rated at the prop.

There are only two motors that I know of that could actually be "up-converted" to the next level easily, and that was the 1992-1994 Force 40 hp; and the older OMC GT 150's - they took a bit more work but were worth it.

But in the end, you are gonna need more power, less weight, and better weight distribution to plane that boat.
Personally, I would start with 25hp.

 

[jimbob669]

Re: Jack plate confusion

There isn't any water in the boat. It's bone dry. Bob: you mentioned replacing the 2x4 deck with aluminum. Wouldn't the lumber be heavier and help the front end level off? Another thing I should mention is that the deck is eight feet long. That may put more weight in the middle of the boat. What about the jack plate though? It is currently adjusted in the middle. How would the boat ride if I adjusted the plate up? or down?

 

[bob johnson]

Re: Jack plate confusion

playing with the jack wont help your bow high problem much if at all...trim and weight is almost all the issue with the bow high...


lightening the load MIGHT allow the boat to go fast enough to get on lane....so even though there is less weight up front, ther eis less weight over all as well....

I wonder why a jack plate is on the boat...if it is a manual..maybe someone has
d a motor with a shaft length that didnt fit the boat.....and they solved it by adding a jack plate....the 5" set back exasperates your problem somewhat...dont know how much...the motor is small and light for a 16 footer....so maybe not at all....

try lightening the load A LOT and what you can't take out, put as far forward as possible....just for an experiment...

get a tiller extension too.....get your butt way up front....

if she gets on plane.....you will doublt your speed....

how much of the boat hull is in the water?????? in inches vertically??

bob

 

[jimbob669]

Re: Jack plate confusion

The previous owner also had a 40 horse that he would use also. I assume that is why the jack plate was on there though I am not for sure. I have never looked to see how much of the hull is in the water. I wouldn't think it would be more than three or four inches in the back. I am taking it out tomorrow for a shake down cruise since I have adjusted the jack plate.

 

[redfury]

Re: Jack plate confusion

The only thing the jack plate is doing for the motor is allowing you to set the height to the optimal position to run the motor with the least amount of drag while on plane, and also allowing you to run shallower without fear of hitting bottom with the prop.

The angle of the motor is key. To far back and the only part of the boat ( with the right sized motor ) is going to be the very rear of it....Youtube has great videos of idiots flying around with the boat out of the water with the motor and the very very back of the boat actually being in the water.

The motor to close to the transom will cause porpoising, or plowing. It's all about the direction of thrust in comparison to the boat as it is riding in the water.

 

[jimbob669]

Re: Jack plate confusion

I have just been calculating the total weight in the back of the boat. I am just guessing at the weight of each object so give or take a few pounds.

Two batteries - 120 lbs
9.9 Nissan two stroke - 85 lbs
Six gallon fuel tank (full) 50 lbs
Bilge pump - 3 lbs
On board battery charger 10 lbs
Me - 385 lbs (I just weighed in at the gym this evening)

Total weight - 653 lbs give or take.

I just can't figure out why the dang thing won't plane off. Is nearly 700 pounds in the back of the boat too much?

 

[bob johnson]

Re: Jack plate confusion

I have just been calculating the total weight in the back of the boat. I am just guessing at the weight of each object so give or take a few pounds.

Two batteries - 120 lbs
9.9 Nissan two stroke - 85 lbs
Six gallon fuel tank (full) 50 lbs
Bilge pump - 3 lbs
On board battery charger 10 lbs
Me - 385 lbs (I just weighed in at the gym this evening)

Total weight - 653 lbs give or take.

I just can't figure out why the dang thing won't plane off. Is nearly 700 pounds in the back of the boat too much?

mildly put...HEEEELLL yes!!!!!!!!!!

you and the two batteries are the big ticket items....

it is only a 9.9!!!!!!!!!!!!!!!!!!!

get a tiller extension and move the batteries......

move the gas too if you can..

other wise, buy a bigger motor

bob

 

[redfury]

Re: Jack plate confusion

mathematically, you probably won't ever get the performance out of the 9.9 that you want on that boat with that weight. How does the nose of the boat sit when you are at a rest? If you are bow high already, the boat is never going to plane.

think of the motor as a jack. The thrust of the motor is trying to lift the BACK of the boat up, not push the front down. If you put 635 lbs in the back of the boat on the trailer, you could lift the front up with a pink, but lift the back up and let us know what your chiropractor has to say about it later.

Distribute that weight evenly in the boat, and you'll find that you can manage both ends of the boat equally. This is why the 18 gallon tank and the driver/passenger seats on my Glastron are in the front 4/5ths of the boat instead of the back. Keeps the nose down ( weight distribution ) and allows the motor to put the boat on plane with minimal effort.

 

[jimbob669]

Re: Jack plate confusion

does anyone have any experience with the Stingray hydrofoils on a small outboard? Would it help me plane off? I adjusted the jack plate to the highest position and it lowered the front end quite a bit. Would a hydrofoil bring it down more and help me plane off? I'm only 200 lbs too. I was just curious if anyone woud call me fatso.

 

[bob johnson]

Re: Jack plate confusion

i am 235 lbs...does that make me fat???

you could still be obese at 200!!!!!!!!!!!!!

yes hydrofoils can help...they usually are really bandaids...but you need a big bandaid!!!!

good lcuk
bob

 

[jimbob669]

Re: Jack plate confusion

You're right Bob. I am 200 pounds but I am only 5'2" so I guess I am overweight. What do you mean "band aid". Will they only temporarily help?