Shearwater Porpoising problem

[paublo25]

First off THIS IS NOT MY BOAT, I am just extremely curious as to why this could be happening. A little information on the boat, Shearwater 25LTZ w/ 300 Merc Verado, hydraulic jackplate, trim tabs, power steering and other stuff not needed for this question. Ok this boat is for my father-in-law and ever since he bought it 3-4 years ago it will porpoise out of no where, water can be glass smooth. He adjusts the motor, and starts using the trim tabs after that, he also lifts the motor up. Now this past weekend I paid attention to the motor while we were running and I noticed something odd to me that I don't remember seeing on other boats that I have ran in. Out the hole water will come up between the motor and hull. While we run when front bounces up and while running flat I noticed water spraying up and away from motor, almost like something flat would be dragging right in front of the motor. Then when we stop before the wash gets to the boat the water will spray up and onto the back of the boat and up almost to the top of the motor. Another thing is this boat is really really slow out the hole. With 5-6 people in the boat, 4 by the center console and 2-3 right behind it, we almost have to move people to the front to get the boat on plain faster. I wish I had pictures but didn't have my phone on me at the time. I'm just extremely curious why this is happening and any would like any of the vets input on this matter.

[redaddiction]

Sounds like the motor is too low in the water.

[Gerald]

Can you post a little more information about what rpm is the engine running and at what speeds. Also what prop is on the engine?

The porpoise problem could be caused how the weight is distributed in the boat. Sounds like the boat is light in the front.

A different prop might improve the preformance....but I am no expert.

[paublo25]

I also thought motor might have been mounted to low also but I'm no expert also. The boat will run around 45-50(on a good day) mph, not sure on the rpm. I know he said its suppose to reach 6800 but he can't get close to that at all. He did say that he is getting a new prop with diff pitch, but he has done this before with no change. Hopefully it will work because this is a great boat but it makes it a pain to ride in most of the time. I wish I had more info on the motor, but from riding in it I have always thought the it felt like we were dragging more motor through the water than we need.

[fishinpox]

generally when a motor is trimmed to high you will have a crappy hole shot and you will also spray a "rooster tail" if the motor is jacked up out of the water. sounds like a re worked or different prop could help also

try this if you are in deep enough water next time: trim the motor down and then get up on plane once on plane trim the motor up , too much will cause a boat to porpoise though

[Bucoo]

I don't know anything on why its porpoising but one thing I've witnesses is that those verados aren't the best for holeshot. Rode in a 22ft shearwater with a 300 pro and it was real sluggish at takeoff.

[barbarian]

The spray sounds like the motor is too low, but that doesn't usually cause the porpoise problem. Could be 2 seperate things going on. I would locate a Shearwater dealer and have them take a look. They should know immediately upon inspection.

[paublo25]

Thanks for the info guys, he is going to change the pitch on the prop first and then work our way back from there. One problem is that he bought the boat directly from Shearwater so now he has a little trouble getting dealers to look at the boat w/o paying out the a$$ for it. With shearwater so far away it usually takes a long time for any response on fixes to problems with the boat, took about 3-4 months trying to get an answer about an electrical problem for the computer(turned out it was just a bad connection). He said he will NEVER buy directly from a dealer again, it is a little cheaper but you get hit with the customer service problems not having them close to where you live. All information has been greatly appreciated, Thanks guys.

[sniper3726]

Changing pitch will not fix it.

[paublo25]

Pitch will help with the RPM problem, what is your take on the porpoise'n problem?

[meaux fishing]

That motor shouldn't run to 6800 I don't think. Most 4 strokes top out around 6000-6100 rpms

[Tonka337]

I had the exact problem with my Shearwater 25TE when I first got it. The deal with the Shearwater is that it needs more bow lift than the conventional bay boat. I've had lengthy discussions with Gill over at LMC in Houston who sells Shearwater boats. Whats actually happening is the boat is trying to get up on it's pad and falling off over and over again. You should phone her and discuss your problem you're experiencing. I currently run a RAV4 blade and a Tempest plus 19 pitch. You should also call the Prop Shop in Lafayette and ask for Ronnie Gilbert. He will work with you until the problem is sorted. By the way, the Prop Shop is under new ownership and these guys are great. P.M. me and I'll give you the contact details for both parties and contact details for John Gerston which is the local Shearwater rep. LMC is also a sponsor of this website which are great people and were the only ones who got results for me when I had issues with the manufacturer. It's a fantastic boat once you learn the in's and outs of it.

[jjam]

Great thread with good info!

I agree, dif things going on. Raise motor and re-prop.

Porpoising = too much motor trim, lower trim til porpoising ceases

Lack o' Hole shot = too much pitch

Motor drag w/ splash = motor too low

and any above combos out of whack can create bad planning attitude!

Good luck, you're on the right track here!

Jimmy

[SuperDave]

Baggy's Prop shop in Houma is another good prop shop. He's a 2nd generation proptoligist.

[ragheadforareason]

to me, if the motor is too low raise it w jack plate. I have the same boat and run it jacked up about half way-most of the time. Seldom use trim tabs. Should always come out of water trimmed all the way down. not sure what prop is on mine but I'll check next time I'm near it, may be next week. Good luck

[TNP]

Rode in a friends SW last fall. Boat porpused all day. finally asked WTH are you doing, let me drive my BW doesn't do this. Didn't help. This hull seems to very sensative and the importance of having the right pitch and rake on your prop is very critrical. Most people buy a rig and tell the dealer they want top end. True, it will run 65 MPH, but take 300yds to plane and you have to run 45 to keep it on plane b/c you have 2 much pitch.
By far, the most critical thing you can do to a boat is prop it right. Took me 4 props on my zuke 250 to get one with hole shot, mid range performance and fuel economy. Call the good folks at Power tech props. They have a great selection of props and you can return one if it isn't perfect. Good Luck..TNP

[thunderstruck]

Try Ken at www.propgods.com out of Fl. He has a try before you buy program that is easier than easter egg hunting for props. He propped my 24 Triton w/ a 250 verado the first try. Lots of bad advice on props out in the market so really the only way is to try a few without getting too skint up!

Porpoising is not an easy problem. My brother fixed his pathfinder with an adjustable jack plate and a 4 blade prop.

BTW Verado WOT rpm range is 5800-6400 rpm. Need to prop to hit that rpm at WOT no matter whether you run WOT or not. Verados will push gasoline past the rings into the oil if you lug them down with too high a pitch prop.

See www. veradoclub.com for all you ever wanted to know about Verados and props.