28 porpusing BAD!!!!!
 

My brother in-law bought a 2001 28 Sonic with 6.2L small blocks. The problem is that at cruise 3000rpm the boat will not settle down, he has tuck the drives almost all the way in and run the tabs down which is killimg the fuel mileage and speed. Props are 24 Bravos and has also tried 23 mirages doesnt seem to matter that much.

Solution thought to put a drive space in, thinking that the props are to far out of the water and are causing this.

Has anyone had good or bad results???

Re: 28 porpusing BAD!!!!!
 

Not sure on the 28 but Prowler added a spacer to his 26' add it didn't help. I assume at higher speeds the porpoising goes away? Does he have a notched hull ? I rather doubt that the drives are to high but I'm not familiar with the 28. Steve

Re: 28 porpusing BAD!!!!!
 

Yes, if he runs the boat up towards 4500rpm it goes away some but still has some tab. Just cant cruise at all, the ride just sucks.

Re: 28 porpusing BAD!!!!!
 

well i put the 1" spacer in like steve said,didn't help anything,the only thing it did was made it harder to get on plane,lots of throttle.i faxed dollar last year,no response,just like you bought a used boat when i've had mine since new.the only thing i can think of is the drive is too deep,i'm keeping my eyes open for a shorty drive.if i'm up over 50 mph the boat runs fine,good thing with the upgade on the horsepower i can run 55 mph at 3500 rpm's with a non-labbed 30 pitch bravo-1 4-blade.the 28 might be a total different animal with twins and more weight,goodluck,dave

Re: 28 porpusing BAD!!!!!
 

I have had positive results running a lot of down tab and trimming the drive out. I can run 3200 rpm with min porpusing. Took me awhile to get the boat trimmed correctly but you can get it to almost stop.

Re: 28 porpusing BAD!!!!!
 

We can get it to stop also by alot of tab. I have never owned a boat that I could not cruise at 3000rpm/ 40 mph and constantly have to have that much tab. Something is wrong a boat should not do this. The speed is cut dramatically when the tabs have to come down.

Is the boat not balanced very well? All I know is if he cant fix the problem after this year the boat is forsale.

Re: 28 porpusing BAD!!!!!
 

Tabs down to 5 and trim drives out to 2-3 seems to help alot.
Higher speeds tabs come up trim out . Just the way it is .Mine is a 358

Re: 28 porpusing BAD!!!!!
 

Try running a set of Hydromotive's They will give you more stern lift. Where the Bravo's will give you more bow lift. Talk to Julie she will be able to help you.

Re: 28 porpusing BAD!!!!!
 

i try'd a hydromotive on mine,the prop felt real heavy and didn't do anything to help anything,after 10 minutes on the boat,prop came off and sold it,the only thing that seems to help is a bravo 1 4-blade at lower speeds,higher speeds and all out running a 3-blade mirage works real well.dave

Re: 28 porpusing BAD!!!!!
 

I am not sure if a hook in the hull will cause a boat to porpuse. but it may be worth checking.

Re: 28 porpusing BAD!!!!!
 

Its the notch in the hull. Its always been a problem. The boat gets up on plane, and starts to run, and is looking for that extra notch in the hull to continue planing on, and its not there, so the boat 'falls off'. Best bet is to have that notch replaced by a professional. The notch has been there for years to put the props in 'cleaner water' but now that boats are running faster then they were when those hulls were designed, its somewhat of a hindrance to performance.

The boat is either always going to need tab to keep away from the bounce, or just can't spend long at mid-range speed.

Re: 28 porpusing BAD!!!!!
 

I don't understand. I had a 28ss with 350 EFIs, and I never had that problem. At 3000 rpm I was going 40 to 42 mph (GPS) with the tabs at 2 and the drives tucked in. Fuel was about 13 gph. The only time it would porpuse was WOT and drives out (about 65 to 68 mph). There must be something in the hull along the keel.
Why don't you call Bruce at Sonic?

Re: 28 porpusing BAD!!!!!
 

I owned a 28 with big blocks in it. The 28 does not require that much trim on the drives probably 1 to 2 at most. The tabs I set at 2, which in my boat was just below the bottom of the hull. On my boat, 0,1, was negative tab. This is just the way my previous boat ran. As speed increased I raised the tabs not the drives...

26 Prowler need help
 

I have the same problem with my 26 Prowler. I am running a Bravo 1 Four Blade with a 22 pitch. I have a newer 496 HO with the Turbulators removed and I am hitting the rev limiter at full throttle. I am only getting 59 mph on the gps so I have to think something is wrong? I called Sonic today and they said I could run a 26 Bravo 1 with that motor? Any help. Please email me @ [email protected].

Please help

Re: 28 porpusing BAD!!!!!
 

I have seen a nose cone fix the porpoise and chine walking on a Checkmate Convincer. It only had a 330 so high speed wasnt the issue. The nose cone settled the ride nicely. Might be something to try.