12' Aluminum V-Hull - Issues porpoising and planing

[BananaMan]

Good Evening Gents!

I have an older 12' v-hull princecraft

I reached out to princecraft to try and figure out the exact year but their records don't go back that far.

It is rated for Max 15 hp and max weight of 710 lbs.

I recently upgraded from my 6hp 1975 evinrude to a 2024 tohatsu 9.8
I couldn't get on plane with the 6 hp and wanted to have a bit more speed to get to my fishing locations.
I realize the older 2 strokes were much lighter than the new four strokes. Could this be the main contributing factor?

The issues I am experiencing with the 9.8 (80 lbs) - and only myself in the boat (180lbs)

- The boat catwalks like crazy at low speeds. So much so that it's close to taking on water at the stern. I have tried all the trim positions and it seems to make no difference.

-The boat planes out once I get over half throttle or so. But, at this point it starts porpoising. Again, this is constant on all trim positions.

My fix - I put 2 large tree stumps in the bow as I had just finished cutting down some birch tree.
This fixed both issues.
I got up to 32 km/hr - nice smooth ride.
However, it is very cumbersome to have to move these in and out when I do have a passenger. Also, they aren't super stable and vibrate around a bit.

My questions

1. Is my motor and myself too heavy for this boat?

2. Is there a better fix than putting weight in the front? I will opt for bags of sand or gravel if this is the best option.

3. Am I missing something completely?

I can provide some pictures If necessary

Thanks Folks!

 

[Scott Danforth]

1 maybe
2. NO
3. 4-strokes are heavy as phuck

A 12 foot boat is supper supper small. As in 1 person and a dog small. Plus it's narrow, so you need to move weight around as you found out

Your 710# rating is for people and motor and gear and fuel and beer.

9.8 tohatsu is 83#
3 gallon fuel tank is 25#
You 180#
Anchor and rode 25#
Fishing gear 25-50#
Oars 20#
Case of beer 40#

That leaves room for another 180# person

However you have to balance the weight

So either keep up with adding weight, or when it's just you, use a tiller handle extension and move forward about 2 feet

 

[Grub54891]

Put your battery and fuel tank as close to the bow as you can. Small boats are subject to load. My duck boat requires the fuel tank and battery just ahead of the back seat.

 

[Texasmark]

Besides moving things forward, including your position if possible....I doubt it on a 12' V hull, adjust the "trim" position of the lower unit with respect to the transom via the tilt bracket slots on the engine. Proper trim can solve a lot of sins.
I ran a Merc. 7.5 on a 10' Lowe Lake John (boat) and fished alone. That combination ran out real nice, planed easily and gave a comfortable ride with tiller steering, but there is a huge difference between my boat and yours.

Mine was flat bottomed with good width and offered a good planing surface for water to push against to get the transom up, increasing speed....which is one of the ways you solve porpoising problems. Yours probably has rounded chines, isn't all that wide and you don't have a lot going for you to "get the stern up"......so you have to move gear and if necessary as others have said, add a cinder block to the bow area or put more beer in your cooler after you move it forward.

 

[dwco5051]

Have a 12' Meyers 12' I run mostly on electric only lakes. Oldest boy bought a 5 hp Merc cheap and put it on. I put a 5 gal dry wall bucket between the bow and the front seat and just added water for ballast. About a half bucket (about 20 pounds) was the perfect amount for best handling. Adjustable for weight, easy to transport an empty bucket, and cheap. Ships have used water for ballast for years and it still works.

 

[racerone]

Try a ---" whale tale "---device on your motor.

 

[airshot]

Not a fan of tails but in extreme cases, they do work !

 

[racerone]

I agree.-----Have seen whale tales on boats and motors.----Promotional material makes folks think it will cure everything.

 

[JimS123]

Certainly, move needed items around, but never add extra weight.

I fixed the same problems eons ago with a set of Perko "fixed" but adjustable trim tabs. About 40 bucks as I recall. But they don't make them any more.

Last resort is a hydrofoil. Don't buy a whaletail, buy a Doelfin. Best 40 bucks you'll ever spend.

(Not a good picture of the Perko, but its all I have. You can see it under water next to the pitot tube.)

 

[Scott Danforth]

any hull mounted tab that extends the running surface works well. they used to sell aluminum pods that did the same thing.

 

[DeepCMark58A]

I have a pair of vintage step and trim NOS trim tabs was saving them for just the right hull. Agree if you want to do it properly by trim tabs, a plastic fin will only help you porpoise slightly less.

 

[BananaMan]

Was checking out the Doelfins on YouTube today. Seems some people have had major success with them.

I bought 2 - 50lb bags of sand. $8

They fit right under the front seat quite nice.

The cat walk is gone and it's not porpoising at all.

I am getting speeds up to 33 kms (20 mph)

I think for now the sand will do the trick while running solo. Easy enough to move out when I have a passenger.

Thanks for all the tips!