snave8

Update:
Ran the boat today with the Rev 4 23P. Unfortunately I couldn’t find any really calm water…….anywhere from a 6” to 12” chop.
So far the only improvement with the Rev 4 is that the boat literally leaps on plane…Major improvement there but……
Still cannot raise the tabs all the way at full throttle, the second I do, the boat starts to porpoise. Don’t get me wrong, they are only slightly down….Can barely see any spray coming off them, but just enough to limit the top speed to 64 or 65 MPH.
I can plane the boat out, and run up to 25 MPH without tabs, but anything over that (without tabs) and it porpoises.
At high speed when it does start to porpoise, on the fourth cycle it dives and rolls to the left.

The bottom is straight as an arrow. Used a 4’ straight edge to measure the aft 10’ of the hull….No problem there.

The centerline of the prop shaft is 7 1/4” below the low point on the keel, measured with the drive in neutral position,

The outdrive is centered exactly on the transom

Measuring whether the outdrive is perfectly vertical is kind of tough, but measuring it in relation to various places on the outside of the hull yielded MAYBE a 1/16” inch variance, which could vary well be attributed to not measuring it in exactly the same place side to side.

So unless the drive is mounted too deep at 7 ¼”…….I give up.

Mark

SB

iTrader: (1)

This is starting to sound unbelievable. Any other 22 Classic owners in the area that can go for a ride with you. Sometimes, two brains are better than one..sometimes not.

Pat McPherson

So strange! Did you check the bottom of all 4 lifting strakes and the chine?

Pat McPherson

I recall my drive is set very deep also in the 7" range. There are lots of guys running shorty but have no idea if that would help.

Pat McPherson

Did you check the spacer in the dive where the Pistons connect. It should be set so that the drive can tuck in past neutral to push nose down. I can't understand why you can't trim the drive down to get rid of it he porpoise

Pat McPherson

If there is nothing obvious wrong with the hull or drive set up. Try putting 1 or 2 sand bags up in the bow. Racers do this to keep the bow down in the rough so they don't use lots of tab and scrub speed. Around here Hardware store carry "tube sand" it comes in a rugged canvis type tube that won't break easily. People put in cars and trucks during the winters. I've had a number of these style hulls including 3 Donzi and never experienced your issue. I do know of a 24' Pantera that had 200# of lead bolted in the bow to keep the nose down though.

snave8

Yes, as far as I can tell, everything is straight.

snave8

The drive tucks in past neutral.
I can keep it from porpoising by leaving the trim down, but the boat isn't going to go anywhere near top speed by doing that.
Believe me, if I just want to cruise around in the boat in the 20-60 MPH range the boat is fine.....But there is no way of reaching top speed with the trim down, or the trim up, but dragging the tabs........I bought the boat to go fast!!
I'm going to take the boat to a high performance boat shop in Lake George, NY. The owner claims he's had two customers with 22 classics, with the same problem as what I'm experiencing......Both were solved by raising the prop height with an IMCO. He has a used drive he's willing to let me try before buying it.
I'm also going to have the entire hull and drive mounting checked out while it's there.

Mark

Pat McPherson

Good Plan! Need to get other eyes on the boat...

I believe the newer 22C have the outer lifting strakes wider apart because the stringers are wider for the 496/8.1 engines... I believe this to be only difference between your boat and mine...

Did the shop tell you what year boats also experienced this issue?
Wondering if it's boats with the wider stringers/strakes...

I'm planning to down size from my 22 to an 18 so not really looking to go to the shorty but I would like to know what the speed increase would be? 7+" below the bottom is really deep...

snave8

I can't believe I didn't think of trying that sooner. I put two 60 lb bags in the bow, ahead of the storage compartment . Unfortunately once again, the lake was a washing machine yesterday, but I was able to get to 60 mph with the tabs up for a short period of time before running into a big wake that started the dreaded porpoise going.
While crawling in the bow I was surprised to see how far forward the fuel tank is mounted. That would explain why the porpoise situation gets worse, as the fuel level decreases......Also it providing me with some hope that adding bow ballast might help/fix the problem.

Mark