22 Classic Help!!
 

I started a thread a while back about some of the issues I was experiencing with my new boat. This thread deals with a specific issue so I thought I'd start a new thread. I've also posted this to the Donzi Forum.

I recently purchased 22 Classic Anniversary Edition with a 496 Mag/Bravo One.
Compared to where I started out, I'm much more comfortable with the boat now. I switched the Bravo One prop that came with the boat for a Turbo One 25P.
The boat seems too handle better overall and I picked up a couple more MPH with the new prop but.........Here's the problem: I'm getting an extreme intermittent porpoise that starts at 63MPH.
I'll take the boat out with 4 adults in light chop and she'll do 67mph the whole length of the lake. I'll take the same people out the next day in the same conditions, and can't get over 63 before the boat starts to develop a severe porpoise.
I know this is a drivers boat, and believe me...I'm drivin it. I'm a commercial seaplane pilot, so I'm used to operating complex machinery, that requires constant control inputs on the water.
Here's what I'm doing, and what happens:
I typically run the boat with an eighth up trim and tabs halfway down for normal cruising (25-40 mph). Any less tab than that and the boat porpoises. When I want to go wide open, I open the throttle, raise the tabs all the way up, then trim to max speed. This configuration puts the bow WAAAAY up in the air, leaving just a few inches of the transom in the water. Some days everything goes well (although it's a scary ride when I encounter boat wakes) and some times at 63 MPH the boat develops a NASTY violent porpoise, with each cycle getting progressively worse, with the bow going increasingly lower, to the point where I'm sure, if let go, it would stuff. The only way to stop it is reduce power and aggressively down tab.
The only way I can go anywhere near top speed consistently, is to leave the tabs down slightly, but this knocks 3-4 mph off my top speed, and even then, I have to drive with my hand on the trim tab control, so I can immediately drop the tabs at the first sign of porpoising
Fuel level effects this also. with full fuel, the porpoise is less likely to develop, and when it does is less severe.
When I first got the boat, I ran it out of gas (When the gauge reads 1/4, there's about 1 gallon left in the tank). In any case, I put 5 gallons in it to get me home. I figured I'd see what she'd do with just me and 5 gallons aboard. Couldn't even go 60 before it would porpoise uncontrollably.
I've owned high performance boats all my life and have NEVER experienced anything like this. Obviously they're not all like this, so I'm wondering.......Do I have a bad hull possibly? could the drive height be wrong when it was installed. Should I try a different prop? The bravo one caused the boat to chine walk and porpoise some, but nothing like it's doing now,.........Help!!
Mark

I don't have any porpoise issues at all. I mean I can induce it at low speeds but if I trim down it stops. Never an issue at higher speeds. A few boats left the factory with the drive slightly off center. 1/4" can cause problems. Start by checking that.

Have you tried using a straight edge on the hull to determine if you've got a rocker issue?

Not yet, but I'm going to this weekend.
just curious, if that's the problem, what's involved in fixing it?

Depends on what you find; could be as simple as a little grinding or as much as reworking the entire hull (the "blueprinting" you may have read about). Have you posted in the Fiberglass forum here on OSO?

Have you posted over at http://www.donzi.net/forums/index.php ? There are some experienced 22C owners there too.

I see you are a seaplane pilot. What do you fly? 208s or Twin Otter floatplanes? Or maybe oldie Grummans?
Sorting out your hull isn't that much different than getting the ac weight and balance right, there just isn't an app for it, yet!

Yes, posted the same thread over at the Donzi Forum.
I fly a Lake Turbo 270 Seafury.

Mark

The shorty advice probably won't cure your issue but you will probably be happy with one anyway. A lot of us run those. At least one of the "problem" boats mentioned had the drive installed off center.

Following

Is the Turbo prop what others with your boat are running ?

My only experience with a Turbo prop was on a light weight 20ft boat and wholly schit did it provide bow lift. Way too much for this boat. When you would use the trim, the outdrive would not move in relation to the water, the boat would just lift....like the whole damn boat. Scary actually.

Props can make or break how a boat drives.

Yes it can but the 22 Classic hull should not have any bad handling characteristics at speed with any prop. I'm running a BBlades 30p Bravo 1. The Bravo 1, Turbo and Mirage plus are all common on these boats and will not induce porpoising or chinewalking. I'd say the M+ is the most common prop and is what they come with from the factory, or at least they used to.

+2 on checking the bottom to see if there is a hook or rocker. +2 on check drive center and straightness. I think it was also suggested to check the slop in the steering system...

My boat will porpoise at low speeds but can correct with trimming down. I don't need tabs. I only use tabs to correct an unbalanced load or to keep the bow down in rough water.

Other props to try - my boat came with a Mirage non-plus and she handles OK. I like the Mirage non-plus better than the newer Mirage plus; I think the difference is in the cupping. I tested the Turbo 1 and Turbo Vector and both worked OK; not all that different than the Mirage and Mirage plus, I liked the Turbo 1 best of the 3 blade props I tried.

The best prop I've tried is the Merc Revolution 4; this is what I run...

I'm going to try some different props before I go any further. I talked to Bret at BBlades, he suggested the Merc Rev 4, so I'm going to try that in a 23P under their test program. I have little if any confidence that any prop is going to cure the awful handling of this boat. I hope I'm wrong.
I get what to look for on the bottom, but what exactly should I measure on the drive? Just make sure it's centered? Is there a reference point to measure from?

Mark

I run a 14.25 diameter 3 blade 23 rapture and it handles great at all speeds.. I have an 87 22 classic Limited with a 454/330HP Alpha. It is a stock boat. The X on this model is raised a bit more than in the other models..Haven't had an issue with proposing or chine..

I'm going out on a limb and betting the Rev 4 is going to help you a lot. I'd test the boat with on you, the driver, and maybe one passenger. Don't touch the tabs, leave them up and just use drive trim.

Use a long level or straight edge to check the bottom at each strake and at the chine.
To check center, I'd just measure from each side at the chine to the drive transom assembly.

I certainly hope you are right. I have a 6' level to check the bottom with.
As far as not using the tabs, I'll give it a try with the new prop but so far, it's been impossible to not use them. Just to be clear, this is not the type of porpoise you see where the boat is happily lopping down the lake with a steady bow up, bow down rythem. The porpoise I'm experiencing is impossible to "drive through". It's sharp, rapidly developing cycles, where the bow takes an increasingly lower and lower attitude when it contacts the water with each cycle. If I were to let it go, the bow would eventually stuff, even in calm water. It's downright scary and dangerous.
I've seen video of a classic running in the low 80's while porpoising, but it's a steady and even (for lack of a better term) porpoise. Nothing like I'm experiencing. With the previous Bravo One prop it wasn't anywhere near as bad as with the Turbo One....As long as I had over half a tank of gas. Below half the boat handled progressively worse as the fuel level went down. With 5 gallons in the tank, I couldn't go (safely) past 58 Mph or so.

Mark

You should be able to run at any speed with tabs full up in calm water or in small chop. Tabs should only be needed to correct an unbalanced load or slight lean from prop / engine torque. There may be a speed range you can't adjust trim to smooth the ride but I've only experienced that at lower speeds, like 30ish... If you can't drive 60+ without tabs with a Rev 4 then there is definitely something wrong with the hull or drive setup... The boat really shouldn't be that hard to drive... My wife drove ours last weekend at 60+ with very little instruction for adjustments...

In my original post I mentioned that I can run up to 63 mph with the tabs down, with not much trouble. The problem occurs when I raise the tabs to obtain top speed. The boat immediately starts to porpoise.....Although not always....The severity seems to be related to how much weight I have (fuel and passengers) in the boat.
Here's my original post:

I recently purchased 22 Classic Anniversary Edition with a 496 Mag/Bravo One.
Compared to where I started out, I'm much more comfortable with the boat now. I switched the Bravo One prop that came with the boat for a Turbo One 25P.
The boat seems too handle better overall and I picked up a couple more MPH with the new prop but.........Here's the problem: I'm getting an extreme intermittent porpoise that starts at 63MPH.
I'll take the boat out with 4 adults in light chop and she'll do 67mph the whole length of the lake. I'll take the same people out the next day in the same conditions, and can't get over 63 before the boat starts to develop a severe porpoise.
I know this is a drivers boat, and believe me...I'm drivin it. I'm a commercial seaplane pilot, so I'm used to operating complex machinery, that requires constant control inputs on the water.
Here's what I'm doing, and what happens:
I typically run the boat with an eighth up trim and tabs halfway down for normal cruising (25-40 mph). Any less tab than that and the boat porpoises. When I want to go wide open, I open the throttle, raise the tabs all the way up, then trim to max speed. This configuration puts the bow WAAAAY up in the air, leaving just a few inches of the transom in the water. Some days everything goes well (although it's a scary ride when I encounter boat wakes) and some times at 63 MPH the boat develops a NASTY violent porpoise, with each cycle getting progressively worse, with the bow going increasingly lower, to the point where I'm sure, if let go, it would stuff. The only way to stop it is reduce power and aggressively down tab.
The only way I can go anywhere near top speed consistently, is to leave the tabs down slightly, but this knocks 3-4 mph off my top speed, and even then, I have to drive with my hand on the trim tab control, so I can immediately drop the tabs at the first sign of porpoising
Fuel level effects this also. with full fuel, the porpoise is less likely to develop, and when it does is less severe.
When I first got the boat, I ran it out of gas (When the gauge reads 1/4, there's about 1 gallon left in the tank). In any case, I put 5 gallons in it to get me home. I figured I'd see what she'd do with just me and 5 gallons aboard. Couldn't even go 60 before it would porpoise uncontrollably.
I've owned high performance boats all my life and have NEVER experienced anything like this. Obviously they're not all like this, so I'm wondering.......Do I have a bad hull possibly? could the drive height be wrong when it was installed. Should I try a different prop? The bravo one caused the boat to chine walk and porpoise some, but nothing like it's doing now,.........Help!!
Mark

I read your post Mark. Your boat should not be that sensitive to weight and should not need tabs to run without bouncing all over. Check the bottom for straightness both sides at chine and both sets of strakes. Try the Rev 4 prop. One other item to check is the spacer in the drive were the bolt connects the trim Pistons; it should be to the transom side so the drive trims deaper...

Do you have indicators on the tabs. Have you ever run the boat wher you feel comfortable and don't move the tabs. Take it out of the water and see where they really are compared to level. Maybe your just running too much tab keeping the bow down and lifting the rear up out of the water. I would start a run. Tabs up all the way keep the drive trim in and trim up to level only. Do it very little at a time and give the boat time to react and settle at each stap of the button. Check and mark that adjustment also. So you really know where level is. Last thing. Bravo drive. If it's a newer model with ecentric adjustment at rear ram connection. Make sure it's at the most rear setting. This often gets moved when taking the drive off. Let us know how it goes.

Or bolt some lead way up front.

Class6 has similar advise as I and maybe explained it better. Small adjustments of trim to bring the bow up and only use tabs if required to level the boat. Many times when I run with just one on board the port tab is down a little when I pull her out on the trailer. This is do too the roll the boat has from a right hand prop and weight on port side. When I run solo no tab required to stay level; my weight balances the roll from the prop torque. I find with a 3 blade you can easily over trim and the boat can become vary loose. With the 4 blade Rev 4 I can trim to the moon and the boat just slows down if I over trim. Again, you should not need tabs to keep the boat from porpoising... The lead weight idea works well if you feal the need to run wild in rough water. It keeps the bow down without using lots of tab and scrubbing speed...

The boat will porpoise with out using the tabs at lower speeds no matter where I start or end with the trim. At around 40 mph I can raise the tabs all the way up (in calm water), until I get into the low 60's, where it starts a violent porpoise. In order to run in the 60's, I need tabs, unless I have the boat weighted just right I haven't yet figured out how much weight and where though.
I appreciate everyone's input here.

Mark

Forgot to mention, no, I don't have trim tab indicators. If I keep the boat, I'm adding them next season though.

I realize your a pilot , so this may sound like a dumb question. Have you checked trim tab wiring,( are you sure they are going the direction indicated on switch?) Tabs down with drive trimmed up will cause bow lift ,then nose dive.Good Luck!!!

Sorry Man, it should not be this hard to run...
 

Try the Rev 4.If it doesn't solve this problem of needing tabs, there is a problem with the hull or drive setup...

LOL....Yes!!

You shouldn't need them. Especially if you have auto retract; Then you always know you are starting out full up.

Above in bold is concerning. Have not witnessed this in any boat. Chine walking, yes, but violent porpoising ? No.

No auto retract.....Have to install the LED indicator/actuator switches to get that. They are Lemco Edge Mount Tabs.

mark trim guage when drive is PERFECT level and on plane w hull , try other prop / drive boat w drive level to get feel for it / we have way too much tab trim unless u poppin on plane w tabs down / have seen tabs mounted so they drag always fishers cruisers / drive boat w tabs hard up to get feel / check drive see if it tucks in may need adjustment or shorter ram / check boat for issues // check tabs see if they move up out hull plane line / I have used stingray stabilizers don't laugh bolted on they do help xr111

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

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.

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

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.

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

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.

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

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

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...

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