Need help with Porpoising New Crestliner Boat

[JUS1MO]

I recently purchased I New Crestliner Retriever Deluxe Jon boat with a Mercury 60hp 4 Stroke Tiller. We went riding yesterday and breaking in the motor. Water was calm so I ran WOT for a short time and the boat started slight porpoising before even started to trim it up. The weight transfer is as set up by Crestliner, two batteries in the rear, 6 gallon gas tank in the rear, trolling motor on front. my wife was sitting in the front. All normal arrangement of all boats I have owned. This is the first boat that i have owned that has this problem. Hope someone her can help me.. Thanks in advance...

[KennyVexus]

Make sure that the motor is trimming all of the way down. There may be a limiting bolt (thrust rod) in the wrong bolt hole pattern. Located near the trim pump. If all else fails you may have to add trim tabs on the back of the boat. Good luck!

[JUS1MO]

Kenny,
I checked that limiting bolt first thing, not the problem. I think it is just the design of this boat. Since i started researching, this problem is not that unusual. I wish I had checked this out before buying, but never had this situation before. Many years ago I had a 21 foot Key West that had trim tabs that came from the factory, I guess. Actually the tabs were quite nice at balancing the weight and trimming up for speed. I believe I will go that route again with this one. Thanks for your reply..

[KennyVexus]

Kenny,
I checked that limiting bolt first thing, not the problem. I think it is just the design of this boat. Since i started researching, this problem is not that unusual. I wish I had checked this out before buying, but never had this situation before. Many years ago I had a 21 foot Key West that had trim tabs that came from the factory, I guess. Actually the tabs were quite nice at balancing the weight and trimming up for speed. I believe I will go that route again with this one. Thanks for your reply..

My first boat was a 16'9" (V17) Tracker with a 80 hp Merc. It would porpoise as well. I move the trolling batteries to beneath the seats and loaded my heaviest gear to the front compartments. That helped mostly. When I complained to Tracker about it they installed wedges on the chines to pull the front down. It knocked my speed way down so I removed them. Good luck and let us know if tabs helped.

[T-Mac]

I'm going to guess that boat has some tabs sticking back past the transom...(extension of the hull running surface).
If those are present, they are adjustible. They are to be manually adjusted (bent) downward as needed to avoid porpoising.
Rudimentary trim tabs.

[JUS1MO]

I'm going to guess that boat has some tabs sticking back past the transom...(extension of the hull running surface).
If those are present, they are adjustible. They are to be manually adjusted (bent) downward as needed to avoid porpoising.
Rudimentary trim tabs.

Yes, I do have the tabs you are referring to. I have not done anything with those. They are only 1 1/4" X 3 1/2", can't possibly do much. I ordered Lenco Edge 9"X9" trim tabs, i know they will work.. Thanks....

[csurp]

Yes, I do have the tabs you are referring to. I have not done anything with those. They are only 1 1/4" X 3 1/2", can't possibly do much. I ordered Lenco Edge 9"X9" trim tabs, i know they will work.. Thanks....

I think you would be surprised how effective adjusting those tabs can be. They have been installed on some jon boats for a long time. I think I first saw them on the NOVA Jon.

[alanhore]

I think you would be surprised how effective adjusting those tabs can be. They have been installed on some jon boats for a long time. I think I first saw them on the NOVA Jon.

[T-Mac]

Ok. Whatever, I guess (?)...But, the exact purpose of those factory tabs is to adjust and eliminate porpoise. They are found on many brands.
Unfortunately, you could have saved a lot of money.

[FloridaFlyer]

Ok. Whatever, I guess (?)...But, the exact purpose of those factory tabs is to adjust and eliminate porpoise. They are found on many brands.
Unfortunately, you could have saved a lot of money.

THIS IS EXACTLY RIGHT. We have a lot of this type thing down here to allow for low speed shallow running.

These type of things work. My Ranger RT has a couple of very small angle metal strips... VERY SMALL . and Ranger installed them for exactly this reason. I also have know of other aluminum owners adding a little bead of JB Weld in the back to help with the porpoise issue.

[FloridaFlyer]

EXACTLY RIGHT..

My friends and I have had a LOT LOT LOT of experience fooling with this technique.

[T-Mac]

THIS IS EXACTLY RIGHT. We have a lot of this type thing down here to allow for low speed shallow running.
I also have know of other aluminum owners adding a little bead of JB Weld in the back to help with the porpoise issue.

Yep.. I sold jons with jets (O/B's) on them for years --- it often doesn't take much at all. Some Jons have a small hook welded into the hull, at the transom - on each side,and that works fine, too. But some with the factory bendable tab sometimes need quite a bit of downward bend.

[pdcjohnson]

I’ve done the JB weld trick on a few boats it works great and is easy and cheap but lasts and you can file it down to get it just rite. I used JB steel stick its a two part putty just sand 8” on the very back edge of the transom on each side whip it down with a cleaner, mead the two parts together and roll out an 8” x 1/2 “ bead and work it in and let it set overnight. When you test it just keep filling it down little at a time with a file/rasp till you get it where you want it.

[csurp]

These may have fallen out of fashion, but I once brought the nose down on a 17-ft Alweld Jon boat with these wedges. Motor was a 40 Yamaha 2-stroke.

https://www.amazon.com/T-H-Degre-Pos...40942804&psc=1