PDA

View Full Version : Porpoising



Phil
11-05-2003, 06:51 AM
I just bought a 32 foot Grew Power boat. It is equipped with twin 496 H.O. and twin tabs. The boat seems to porpoise alot, and I have to put the tabs down all the way to get it to level out. Is this normal? The Dealer I bought it from says "since it's an off shore design this is normal."
Im wondering if there needs to be more weight up front.
Please help.

Havasu Cig
11-05-2003, 08:01 AM
That is not normal. Our Top Gun does not porpoise at all, and it has very little weight in the bow because it has a minimal cabin.

CAHotRodBoy
11-05-2003, 04:12 PM
Definitely not normal. Offshore don't porpoise unless something is wrong. Could be not enough bow weight. How quickly does it plane out? Do you need full trim and tabs to get it to plane?
Does it porpoise at all speed or just a certain range. Some boats like to run at higher speeds and do porpoise until you hit the “sweet spot”.

SoCalOffshore
11-05-2003, 08:53 PM
That is not good. Take it back and get your money back.

SoCalOffshore
11-05-2003, 08:55 PM
I may be wrong, but I think that Power Boat Magazine tested the Grew and had some issues with the ride.

gnarley
11-06-2003, 09:39 PM
Sounds like the props are wrong & can't hold the bow out of the water & it continues in a cycle up & down. I'd talk to a good prop shop & ask them what they think would cure it. I would think that more cupping in the prop or even larger diameter may cure it but you will need to give your prop shop many numbers for them to help you & may end up spending $500 to $1000 to fix the problem or even more if these props are just the wrong blade to start with.

Dr. Eagle
11-06-2003, 10:20 PM
Originally posted by Phil
I just bought a 32 foot Grew Power boat. It is equipped with twin 496 H.O. and twin tabs. The boat seems to porpoise alot, and I have to put the tabs down all the way to get it to level out. Is this normal? The Dealer I bought it from says "since it's an off shore design this is normal."
Im wondering if there needs to be more weight up front.
Please help.
My 30' Eliminator never ever porpoised, chine walking...now that is another story. I think you may be right, you may need some ballast up front. Regardless, the dealer is FOS....it is not normal...

Havasu Cig
11-07-2003, 06:23 AM
Make the dealer fix the problem. If you start messingwith props, x-dimension ect.. it can get expensive.
The current set of props I am running have been reworked three times just to dial it in, and this is a boat that ran good from day 1.

Steamin' Rice
11-07-2003, 12:56 PM
Originally posted by SoCalOffshore
That is not good. Take it back and get your money back.
Exactly.....:)

paradigm shift
11-08-2003, 06:04 PM
I think Grew as a manufacturer of performance offshore boats is pretty new and that hull is also a new hull for them. The dealer-manufacturer should be willing to work with you on set up to get it right. Give them a chance before you throw in the towel. At the same time make them make it right. The dealer is wrong that it is normal from what you say here. Porpoising is not normal if set up is correct.
Some things that can cause porpoising as a driver is drive trim setting also. You said the tabs are down all the way but what are the drives set at? Are they roughly even or the prop shafts level with the bottom of the boat at speed? Over trimming the drives will cause porpoising also. What tabs are you running. I doupt your problem can be corrected by either of these things alone but just something you can check. Good luck.

bigkatboat
11-16-2003, 09:40 PM
The problem may be in the 'twin engine' weight problem, if the center strakes end in the middle of the hull (front to rear), the tail won't lift. MANY west coast boats can only use the bottom 25% of their trim (drive) because they need the prop tucked in to lift the tail. The tooling was built that way so the nose of the boat would always stay up, and the cabin weight would not try to 'drive the nose in' at high speeds. I'll bet if you had longer center strakes, or small ones from the current ending point all the way to the transom, the boat would 'lay out' across the top of the water much better. You want to 'lift' the boat out of the water, not DRAG the trim plates thru it. ;)

gnarley
11-17-2003, 05:46 PM
Originally posted by bigkatboat
The problem may be in the 'twin engine' weight problem, if the center strakes end in the middle of the hull (front to rear), the tail won't lift.
You want to 'lift' the boat out of the water, not DRAG the trim plates thru it. ;)
A Cleaver style prop would do that, lift the drive end out of the water instead of dragging it.

bigkatboat
11-20-2003, 10:48 PM
Cleavers are not great load carriers and they tend to have a high slip factor. I don't think changing 'blade rake' will do enough to get the hull back on track, either. You need to have the HULL lift itself, and the prop to just PUSH the boat. Back in the 1980's, guys were putting "monster" cams in I/O boats, they needed to get the boat up on plane and a cleaver would give that 'low end slip' that would let the motor get into it's power band. Many of the boats were 'driveable' only above 3000 RPMs, because of the prop slip. You want to go as fast as possable, with the LEAST amount of RPMs you can get away with. Fix the hull.

LHC30Victory
11-22-2003, 05:45 PM
Phil, we have a 30 victory with twin 496HO's and no porpoising! I agree to have the dealer make it right. try to spin the drives inward instead of the usual counter on port, clockwise on starboard. that may give the stern a little extra lift. In any case a well tuned boat will not porpoise except in rare and extreme conditions.

Tinkerer
11-22-2003, 08:15 PM
turning the props in gives bow lift.
turning them out gives transom lift.

bigkatboat
11-26-2003, 11:05 PM
Where are the people from GREW? I am sure they are reading these posts. You can turn the props anyway you like, but the HULL needs work and that's where I would start. Prop rotation is just for 'trimming' the boat's ride, not a CURE for a REAL problem. Please let us know what happens.

Havasu Cig
12-01-2003, 10:24 AM
Turning the props in will make the boat harder to handle around the docks as well. Something else to think about.

powerplay230
12-07-2003, 11:32 AM
How are you making out?
Rich

bigkatboat
12-26-2003, 10:40 PM
We have been waiting for an answer! Has the manufacturer responded to your questions? If you need real help, contact me thru private mail, and I will try to help you out no charge. What ever happens, good luck!

skygod73
12-28-2003, 02:12 AM
not normal.

bigkatboat
02-08-2004, 08:11 PM
Thanks for letting us know what happened, you jackass!

Kachina26
02-08-2004, 08:19 PM
OUCH dude!

Steamin' Rice
02-18-2004, 07:28 AM
Originally posted by bigkatboat
Thanks for letting us know what happened, you jackass!
LMAO.....:D :D

TPI
03-23-2004, 08:38 PM
BKB,
LMAO2.................... He might have replied if you said "send me a PM and I will be happy to help for Double the fair price, and I will lie to you as I charge you by the hour to figure out your problem!:D You are too kind.............................
GT

Hermosa
03-25-2004, 08:55 AM
That hull got some poor reviews. I was looking at the same hull 6 months ago, a bank had one, and was willing to deal with me on it. I wasn't looking for this boat, but the bank I deal with just got it back on a complete property forclosure. I got zero information from Grew, they were in financial trouble themselves. I stayed away... glad I did.

bigkatboat
03-25-2004, 09:18 PM
Any hull can be fixed. I don't know the boat, but maybe we can all work together and correct the problems. If someone out there has one and wants to 'fix it, let us know, I'll help and I am not a "guesser" I just think that if you post a problem, you should post an 'update' or "something"!!