New 9.9 setup - is this enough?

[camdenyardz]

First post so I appreciate the help!

I have a 1996 polar Kraft 1448 and I recently purchased a new mercury 9.9. I thought the motor would be enough to get on plane after reading on different forums and talking with folks, but even with just me in the boat it seemed to struggle. The boat has some decking and 3 batteries.

Any thoughts as to what I can or should do?

 

[FuzzyGrub]

While there are some minor changes you could make/check, a 10HP is not going to be enough. If it was an open rib 1448, without all the decking, batteries, etc, it would still be marginal.

PS: Before investing in a bigger outboard, I'd check all those "bubbles" on the transom. Looks like it has internal corrosion working its way to the outside.

 

[MrGiggles]

I had an Alumacraft 1448 with a 9.8 2 stroke. Decked to the middle bench, a single battery, and a bow mount trolling motor. It would plane with just me, but not two people. As I recall top speed was 15mph or so. I did eventually upgrade to a 25hp but got along okay with the 9.8 for a long time.

The batteries are probably what is killing you. Why three? One group 29 was more than enough with my setup, including cranking the outboard. I had it mounted up front below deck, and had heavy gauge wire running to the rear.

 

[JGibson]

I have a 1648 with a 9.9 and it planes out just fine with 2 batteries, tank and two people. I get up to around 18mph on smooth water.

 

[airshot]

Flat bottoms do create more drag than a V bottom and no real good way to get more hp from that 9.9, add the three batteries and rhe extra weight of the four stroke and decking......you just need more HP, no way around it. My 14' V had a 9.9 converted to 15 hp and got about 23/ 24 mph without 3 batteries and decking. Add hp or trim weight, your call....keep us posted !

 

[camdenyardz]

Flat bottoms do create more drag than a V bottom and no real good way to get more hp from that 9.9, add the three batteries and rhe extra weight of the four stroke and decking......you just need more HP, no way around it. My 14' V had a 9.9 converted to 15 hp and got about 23/ 24 mph without 3 batteries and decking. Add hp or trim weight, your call....keep us posted !

Thanks! Sorry this is a dumb question - when you say converted do you mean bought and sold, or did some sort of chip & carb upgrades I have seen talked about?

 

[Crazyboat]

If you can locate the batteries up front, if not at least make sure you have the engine trimmed in/down. If that doesn't work a lower pitched prop.

 

[sonny1]

That transom needs some loving care.

 

[airshot]

Thanks! Sorry this is a dumb question - when you say converted do you mean bought and sold, or did some sort of chip & carb upgrades I have seen talked about?

My 9.9 was a two stroke, so a simple carb change was all that was needed to convert it to 15 hp. 4 strokes take much more to upgrade the hp.

 

[Pappy]

Flat bottoms do create more drag than a V bottom and no real good way to get more hp from that 9.9, add the three batteries and rhe extra weight of the four stroke and decking......you just need more HP, no way around it. My 14' V had a 9.9 converted to 15 hp and got about 23/ 24 mph without 3 batteries and decking. Add hp or trim weight, your call....keep us posted !

UH.......no.
Flat bottom will always displace less water than a vee bottom and will plane far easier due to the fact that it is flat!

Where are your batteries? If they are all in the stern that can be a big issue. You have to spread weight around. The less horsepower you have the more critical it is.

 

[beagle]

The current Tohatsu / Mercury 9.9 and the 20 are the same displacement. They are roughly 330 cc or 20 cubic inch. The 9.9 has a restrictor on / before the throttle body and according to part numbers, a different ECM. The price of the ECM is, probably not coincidentally, is about the same as the difference in initial cost between the 9.9 and 20hp motors. I'm assuming the different ECM is actually just a different tune, and you really want tuning software which I can't find before you start playing grabass with EFI.

Before I went down that warranty killing path, though, I would do some free / cheap testing. Get a tach on it and verify RPM is where it is supposed to be. It may want less pitch with all the weight. Verify the trim is in the right hole. Does it plow and throw a lot of spry? Does it ride bow high and never plane out? Like has been said, get some weight out of it, or try moving the weight back / forward to distribute it. That wasn't a lightweight (by my standards) jon boat to begin with. If it was decked / framed with wood, obviously much heavier. I'd check the wide open throttle RPM first and maybe consider a smaller pitched prop.

All of this assumes there's nothing wrong with the planing surface of the hull. The last couple of feet need to be very straight if you want it to perform. 27 year old boats tend to pick up some dents along the way.

 

[GYPSY400]

It looks like you simply have too much weight. I'm guessing you have a 24V bow mount, which is overkill. I run a 55lb 12v motor and it's plenty for my 16ft decked out V-hull. So you could eliminate 1 battery that way by going down to a 12v motor.
You can also verify that the motor is in the right RPM range by getting a tach and then adjusting the prop pitch accordingly ( new prop). The motor might sound like it's revving out, but it could be too low to reach peak power.
From there it's weight distribution and trim angle.

 

[FuzzyGrub]

If he is not on plane, he is not even close to the recomended wot rpms. You don't want to make a pitch adjustment based on that low of rpms.

Take the two trolling batteries out, distribute the weight of the starter battery and the fuel tank, and yourself. Retest and see if it now gets on plane. If it does, get a wot rpm and gps speed. At that point, might try to raise the motor some. It looks a little low from the pictures. Not enough to impact getting on plane, but might be holding back 1-2mph at the top end. At that point, wll know about what size prop change might be needed.

If you are happy with the test, than you will have to decide on downsizing your trolling motor or upgrading the outboard. As I mentioned before, it will be marginal, like what Mr Giggles reported. The boat probably planes in the 10-12mph range.

 

[Tbradley]

My SeaArk 1448 riveted hull weights 245 according to the specs. It would plane with a 9.9hp evinrude 2 stroke ONLY with me and gas tank add any more weight, it wouldn’t plane. Upgraded to a Merc 25hp 2 stoke and it plane 5 adults or 29moh by myself.

 

[Stand Up]

I have a 12' jon with a Mercury 9.9 four stroke and if the OB is not sitting down on its final notch, the boat won't get on plane. So, get the motor tilted down all the way and try it. I don't get on plane unless I have the throttle wide open. Also, put the weight of carried items up front and that will help too.

 

[airshot]

UH.......no.
Flat bottom will always displace less water than a vee bottom and will plane far easier due to the fact that it is flat!

Where are your batteries? If they are all in the stern that can be a big issue. You have to spread weight around. The less horsepower you have the more critical it is.

Yes...plane easier, however friction drag from the flat bottom will take more hp to reach the same speed as a V bottom.

 

[wmk0002]

Like mentioned the 3 batteries are probably killing you.

I assume 1 battery is for electric start and 2 are for 24v tolling motor? If so, I'd ditch a conventional starting battery for a motorcycle/atv or lawnmower battery. Those will be more than sufficient. If you dont have a lot of electronics tied to it I'd go with a cycle/atv battery and if you want a little more capacity go with a mower one.

A 24V trolling motor setup is nice but its hard to find smaller 12V deep cycles to accommodate lighter needs unless you go lithium which is expensive. Lithium also comes in 24v models so you can get by with a single battery if you did go that route.

Id try lightening the battery load, getting rid of unnecessary weight, and shifting weight around and see how it performs before doing anything too drastic. If that helps then you can try to re-prop the motor accordingly and nail down a battery configure that works for you but doesnt weigh a ton.

 

[Pappy]

Yes...plane easier, however friction drag from the flat bottom will take more hp to reach the same speed as a V bottom.

Again, not true.
This should be simple. If you have a 6' wide bottom on a boat and one is flat and one is a vee hull which one has more square inches of surface area? Surface area is drag, period. Vee hulls alone have very little inherent lift unless lift strakes are added (that is another hint for you) but they are designed for softer rides since the vee design does not lift and bang over each wave compared to a flat bottom.

 

[airshot]

Perhaps in theroy, but in real life, I have a 12' v bottom and a 12' jon flat bottom, using my 1994 9.9 evinrude the v bottom is faster wot but the jon gets up on plane faster! Shown this to numerous folks many times!! Not going to start an argument here, my proof is in the reality..

 

[Shootstraight]

As others have said weight is a big killer of speed on these small boats. Lead acid group 31 batteries can weigh close to 90 pounds each. If decking is wood especially 2x4 and 3/4” deck that’s a bunch of weight. Even how much gear you bring on a trip affects your speed. My buddies tackle box weighs close to 80 pounds, I’d bet we lose 2-3 mph when he brings that monster.