porpoising sanger... springs?

[davethewave]

'72 sanger starts porpoising around 70 mph. Been dealing with this for a few years now. Tried all different plate adjustments. Could it be
the springs are wore out? It's A dual spring setup.

 

[randyjet]

Never saw weak springs do that they usually will allow the boat to nose over it will slow rapidly and nose drop Flat Bottoms had them hunt but most time Purpose is from Hook in Bottom. Can you over plate and take the porpoise out. But plate set is critical over all plate surface should get a good starting place as suggested by the guys in the Know. I had a Sprint boat couldn't run over 70 without things going south. Talked to JJ beavers he talked to Mike DCucci on setup started there amazing how fast things settled down. Flats take work I have a note book and every adjustment I log and identify cause and affect. I always set my springs just on the other side of loose you can tell and see when the plates drop the speed will fall of and the nose start dropping.

 

[davethewave]

over it will slow rapidly and nose drop ???
I don't get what your point is ! for example." Talked to JJ beavers he talked to Mike DCucci on setup started there amazing how fast things settled down " and
I always set my springs just on the other side of loose you can tell and see when the plates drop the speed will fall of and the nose start dropping. ???? As far as "over plate" hell...I don't know. I have put weight up front and it's a little better I guess but what's to tell from that? Cavitation Plate starting point ? Of course ! A few things i have yet to do is: !) Rudder (shaft is worn at the stuffing box. I slipped some brass shims in to get rid of the slop) 2) Pull and check prop shaft. I have moved the engine forward about 3 inches. Trisd diferent prop location (With nickles). Set springs as tight as possible.
Tried another prop.
This has been going on for like 5 years now (i've had the boat for 40) If I don't get this figured out THIS summer I'm gonna look for another hull. Cole or Curtis . I'll be at Camp Far West look me up .'72 bubble deck sanger 19 foot in need of a paint job. Original rust colored metal flake. If you see A v drive pulling a skier it's probably me !

 

[fastenuff3]

'72 sanger starts porpoising around 70 mph. Been dealing with this for a few years now. Tried all different plate adjustments. Could it be
the springs are wore out? It's A dual spring setup.

try sliding the prop back about 2 nickels and see if it gets better. prop to far forward tries to drive the boat out of water. the only other thing is to add more horse power

 

[davethewave]

Yah, it's probably not the springs. i'm running out of options here. Slight bend in the prop shaft? I've already tried it with the
prop back. It's about 650 HP.

 

[Todd Mohr]

More horsepower will push you past the porpoising, maybe different gears would help. Whats the rpm's at 70?

 

[Dansblown73Nordic]

I had a 19 ft Nordic that would Porpoise like HELL. I tried moving the plate every different way possible. I finally changed the prop. I don't remember why I changed. It totally changed everything about the boat. It lifted the entire boat up out of the water. I won't say the porpoising was completely gone but it made a HUGE DIFFERENCE.

 

[sintax]

I'd try the adjusting the propshaft first, go slow with the adjustments so you can monitor them. Depending on those results (keep track on paper), if you're still not happy I'd return it back to the original and repeat the trial process again with a borrowed prop or two. If you go on Performance Boats forum you'll likely be able to find someone who'd loan you a prop or to for testing. While its not unheard of for plates to be causing this, its more common to be a prop placement issue.

 

[BassLakeCruiser]

HP. I had one of the few Sanger runner bottom race boats. They need the HP to get past it. I tried everything with help of some big name racers and nothing helped. Till we built a hefty powerplant

 

[BassLakeCruiser]

 

[davethewave]

motor is very stout at around 600 to 650 HP. 11 TO 1 V-DRIVE CAM 2 750 holleys Hunt mag

 

[73mandella]

Good thread, but I don't have any suggestions. I have a 73 Mandella (standard deck) and it porpoises long before 70. I keep my foot on the override to bury the nose to make it stop. Some have suggested working on the bottom (about 5k) while others suggest a prop change will help (much less than 5k). I haven't done either. I have a long deck that only needs money to start the rebuild. I'm hoping that the engine being several inches further forward will alleviate the problem.

 

[AzMandella]

Good thread, but I don't have any suggestions. I have a 73 Mandella (standard deck) and it porpoises long before 70. I keep my foot on the override to bury the nose to make it stop. Some have suggested working on the bottom (about 5k) while others suggest a prop change will help (much less than 5k). I haven't done either. I have a long deck that only needs money to start the rebuild. I'm hoping that the engine being several inches further forward will alleviate the problem.

Being a long time Mandella guy , If you have the HP and the bottom is not whacked the prop is your problem . Call Menkins . Tell them what hull and HP and gear ratio you have and they will make a prop with the proper blade size and cupping . The yellow shortdeck in my avatar has a 514ci BBF with about 650+ Hp . Got a new prop from them and it handled like a dream . You need the combo of the HP and prop to keep the bow lifted . I no longer have the yellow boat but am restorring another shortdeck that was my fathers .

 

[davethewave]

I bought a used steel prop to replace the original bronze prop but that was not the answer so I'll try Menkins.How much $ are we talking? I'm guessing
around $800.? I still haven't checked the rod for slop. But you're right about the Menkins..

 

[davethewave]

i just added a tach recently and so far it maxed out at 6k.That's with the boat wanting to fly of course.

 

[AzMandella]

Yeah the $ 800.00 is about right . I was turning 7000rpm with 22 gears and 11-1/2" X 15 prop . Waiting for al things to be done with new Mandella before ordering prop but looking to turn 7000-7500 with 25 gears .