Finally got the first 2 hour break in done on the new engine. It trims to a certain area and runs very smooth. I can trim past that and get 5 to 6 more mph but starts to porpoise. I've read where a hydrofoil will help with that and give you a little more speed. Anyone have any experience with this?

A hydrofoil will stop the porpoising but will also slow you down. More cup in your prop or a different prop is a better fix but a bit more expensive.

I replaced the prop, got a few more mph before porpoising started. Hoping to get a little more.

Need more info on the boat. Make, model, motor, jackplate or no, prop shaft height compared to pad, wot rpms and mph, prop make and specs. I think I hit them all. Someone will come on here and tell you it is a bandaid for a bad setup. I have never heard of a hydrofoil installation resulting in higher top end speed. Must have been a hydrofoil sales person that told you that.

No salesman. Just read online. I have an 18'10" aluminum boat with a 115 4 stroke. I do have some weight on the back with talons. I'm getting about 40 to 42 top speed on plane. I can trim up more and get more speed but the porpoising starts. On plane I'm at 5600 rpms or so.

Replaced the aluminum prop with a 19 pitch prop from Steves

Porpoising is caused by you prop losing its grip on the water and falling down. A fin is not your fix the proper prop is.

I like powertech four blades on iron boats they hold the water better, your handling improve because your prop isn’t cavitating.

Call Josh at Steves prop on fork and let a pro set you up right the first time.

Those talons are contributing to your porpoising. That’s a lot of weight hanging off the transom of an 18’ tin rig.

Watch for any welds breaking on the hull. Bruce’s sons crestliner porpoised so bad it broke the welds. Said he almost sunk it on his first trip out from getting it back from the factory.

I thought a hydrofoil is it or the water when the boat is on plane. If so, I don’t see how it would help.

My opinion is you have the wrong prop or the eight distribution needs some help. Try moving things around in the boat to see if the boat gets happier.

You did the right thing going to Josh. He will get it figured out for you.

with all that extra weight on back this shoud help. put one on mine, faster on plane and a little more stable at speed.

https://bobsmachine.com/product/true-tracker-stabilizer-plate-40-hp/




get a 4 blade from josh and I bet it goes away.

You are right, a lot of weight on a ....19' boat! It is 18'-10" long. A hydrofoil will help.

Never heard of more speed causing porpoising….are you sure it’s not chine walk?

40-42 should be plenty why are you asking for more. Just trim it down.