Boat porpoising, need experienced advice

[FurFlyin]

I bought an Xpress this winter and just finished up a complete restoration with some modifications. I extended the front deck with aluminum to come back to meet the front of the console. I also added a 24 volt Ulterra up front. Prior to beginning the restoration, I took the boat out and it ran great. Got up on the pad and rode like a dream.

When I bought the boat, the trolling motor battery was up front, under the deck. I installed 2 new batteries and an on board charger in the rear compartment.

The boat no longer drives and rides great. Now at WOT if I trim the motor up enough to get the bow and speed up, the boat begins to porpoise terribly. It won't power through it either. I'm having to run the boat with the nose down, which is killing my top end speed.

I do not have a jack plate on the boat. After spending a war pension on the refurb I can't swing one right now either.

Would raising or lowering the motor help?

Any advice?

[PolarKraft195]

Sounds like a weight distribution problem

[Savage33]

Move troller batteries up front. I had the same issue on a seaark that we put a bowfishing deck on. Moved my batteries back to the front and solved the problem.

i understand we are talking 2 different brands. It’s worth a try. Just sit them up there for now and test run it.

[JER-1 BIG BASS]

Believe you answered your own question, you took batteries from front ,put in rear, only major weight change,lost your ride, might been reason batteries were in front

[billnorman1]

You won't have to hook them up to try it. You may be able to add a whale tail to stop the porpoising without moving the weight.

[Luke]

move some weight to the front like has been said. motor is pushing against the back end sitting too deep causing a leverage issue which pulls the nose up then it falls and back and forth and so on. not a huge deal but makes a big difference.

[Skunked again]

^^ What they said about weight distribution. ^^
If you do not want to move the batteries back to the front, a whale tail might help. My first boat had a tail on it, planed out and rode great. I took it off, took forever to plane out, when it finally did, it porpoised. I put it back on.
For what they cost, even if it does not work, your not out too much money.

[FurFlyin]

Motor already has a whale tail on it. I'll try a battery or two in the front compartment and see if that fixes the issue. I'm sure it's a weight thing, but I was pretty sure that I added a balanced amount to the front and back of the boat. The Ulterra weighs probably 3 times as much as the old foot controlled MG did and I also added 2 feet of aluminum deck with 2 more doors.

At any rate, I'll try moving some things. Thanks for the advice.

Only bad thing is, this will mean more wiring! I've spent probably 150 hours working on the boat during the restoration

EDIT: Instead of moving batteries, would adding the same amount of weight to the front of the boat have the same effect as moving the batteries from the rear? I own a truck shop, so I've got group 31 battery "cores" sitting on a shelf that I could move around without having to disconnect anything in the rear compartment.

[alanhore]

Might be worth a try before you tear it all apart.

Motor already has a whale tail on it. I'll try a battery or two in the front compartment and see if that fixes the issue. I'm sure it's a weight thing, but I was pretty sure that I added a balanced amount to the front and back of the boat. The Ulterra weighs probably 3 times as much as the old foot controlled MG did and I also added 2 feet of aluminum deck with 2 more doors.

At any rate, I'll try moving some things. Thanks for the advice.

Only bad thing is, this will mean more wiring! I've spent probably 150 hours working on the boat during the restoration

EDIT: Instead of moving batteries, would adding the same amount of weight to the front of the boat have the same effect as moving the batteries from the rear? I own a truck shop, so I've got group 31 battery "cores" sitting on a shelf that I could move around without having to disconnect anything in the rear compartment.

[Bassnailer]

My brother had similar issue with a Lowe Stinger. It would porpoise unless trimmed way down. He had trim tabs installed and this cured the problem. The dealer put them on, but they were just small aluminum plates in this shape > which were welded on the transom. Easy fix, rides better, and was not too spendy. By brother loves his tin rigs, I love my glass boats. We have the best of both worlds this way.

[Squire]

you might consider a prop change to have one with more lift to keep the bow up. Find a prop shop that will let you try a few and see if this mitigates the problem a bit.

[FurFlyin]

Thanks for all the advice guys, keep it coming!

Does anyone know if raising or lowering the motor a hole would help it?

[FurFlyin]

Is it against forum rules to post a link to another forum? I'd post pictures of my boat restoration but I'm too worn out after posting all of them on the deer hunting forum that I frequent. LOL

[Skunked again]

Adding weight to the bow would be an easy thing to try. Especially if you have those batteries sitting around.

[Enskyte]

Over trimming to get rpms up. Drop a pitch size on your prop. Had the same problem with my tracker.

[BigMouth]

Is it against forum rules to post a link to another forum? I'd post pictures of my boat restoration but I'm too worn out after posting all of them on the deer hunting forum that I frequent. LOL

Copy the image address and use the insert image button above to post them.

[FurFlyin]

I put a group 31 and group 27 battery in the front compartment today and took it to the lake. It's still porpoising. It didn't start at as slow a speed as it did yesterday but anytime I got over about 4200 rpm's it would start.

I guess I'll take both trolling batteries out of the rear compartment and move them to the front and try it again. Any more ideas on what to do?

I don't know enough about chosing a prop to go get one and I don't know of a prop shop around here. I would imagine that there is one somewhere since Lake Guntersville is a widely known lake. Does anyone know of one in my area?

BigMouth, it's not the process of posting them, it's the amount of them I posted. Took quite a while to post a complete series from start to finish on the boat.

[Skunked again]

For the prop, just look up a prop shop, call them. They should be able to help you over the phone.

[375VTROCKET]

Have you tried being very attentive to various trim spots? I have a boat that if you aren't very, very careful you would over trim or under trim and it would do it bad. I learned it's sweet spots but it took a long time.

[billnorman1]

Sounds like you are losing thrust. Cavitation, spun hub, motor height, lack of power etc. Porpoising is frequently caused by lack of power, either through design or malfunction. Since you didn't have this issue before you modified the boat, look closely at that for cause.