Boat Porpoising

[mgsolakis]

I'm having problems with my boat porpoising. Moving some weight forward seems to help. With more weight in the front I can push the boat faster and it planes out but at slower planing speeds it still bounces. Can I solve this with prop pitch or do I have to lower the motor. Any ideas would be great. Thanks.

 

[Old Ironmaker]

Do you have water in the boat or flotation foam may be water logged? Did it plane well for you before now?

 

[Scott Danforth]

What boat, what motor? New problem, or new to You boat? The first suggestion is to trim in a bit.

 

[fhhuber]

see if you can trim the motor down bit more.

Changing how deep the prop/antiventilation plate are probably won't cure it. If the antiventilation plate is just under water when planing height is where it belongs.

porpoising is usually a combination of balance and thrust angle. Changing placement of weight can cure it if you can get enough weight forward.

Not knowing what boat/motor are involved leaves us guessing a bit as to what adjustments are available.

Prop pitch mostly affects what your top speed will be and how well the boat accelerates from a stop to planing. Probably pitch has little to nothing to do with the porpoising.

 

[mgsolakis]

Sorry, I should have given boat info. It's a 1991 Sunray Aruba 16' bowrider. I've always had porpoising issues with it I think because it's rear heavy with out a passanger in the front. The fuel tank, battery and motor are in the rear and the boat has a short front end. Floatation etc. Is all in really good shape.

 

[joe009]

you could try a hydro foil it did wonders for my boat

 

[southkogs]

If it's an outboard, is the trim (typically a pin) all the way in to the transom?

 

[JimS123]

I only had that problem once. It was a combination of a hook in the hull and a motor that exceeded the boat's capacity.

If your boat is properly supported on the trailer and the hull is true, and your motor meets the capacity plate requirements, you need to move weight around. A hydrofoil won't help you.

 

[mgsolakis]

I don't see any hook in the boat. It is rated for 100 hp but the 85 hp V4 Evinrude Outboard I have does weigh some for sure. It sounds like based on what people are saying I need a couple of sand bags under the seats of the bow ride to weigh that bow down more.

 

[Alumarine]

No one suggested sand bags.
People did suggest checking to see if your motor was trimmed all the way in.

 

[mgsolakis]

Sorry, yes it is trimmed in all the way. And down all the way as well.

 

[JimS123]

Adding weight makes no sense. It will hurt your speed and fuel economy. Shifting weight is the answer.

Install a fixrd trim tab that is manually adjustable. Perko & Tempo made them a few years ago. That will solve the problem at the lowest cost.

This is what I mean:

http://www.ebay.com/itm/Vintage-Tem...ash=item33b2fb9a51:g:P-wAAOSwv9hW3brl&vxp=mtr

They made them in a smaller size - I used them years ago for just your same problem. Google e-bay - I'm sure you'll find one somewhere.

 

[H20Rat]

If everything else checks out, move your battery forward... Do you have a side pic of your setup?

 

[milehighjc]

Search for Nauticus Smart Tabs.

I put them on my Crownie 182 with a 5.7L motor. It is stern heavy, but lots of power, and propped for hole shot. Benefits for me included:

• Better hole shot. Almost no bow rise at all, all the power gets directed forward instead of down, so my acceleration is much better
• Much smoother ride in chop. Rides like it is bigger than it is.
• Mitigated bow wander at no wake speed... Really doesn't require any correction anymore.

The tradeoffs:

• About 2MPH off the top end
• Kind of a funky wake for slalom skiing. Not too bad, but noticeable.

Net : Major improvement for me, even though I had scads of power to begin with, and really didnt have a hole shot problem. I was really trying to smooth the ride a little, and cut down on bow wander, and was surprised how much better the hole shot really got.

The are not overly expensive, and easy to install once you get past the mental block of drilling into the boat.

 

[mgsolakis]

Sorry guys trying to get a pic loaded but it keeps saying server busy. It might just be the bad connection I get up here at the cottage.

 

[thumpar]

There is usually a pin on an outboard to adjust how far it can go in/down. Make sure it is set to allow the furthest in/down possible.

 

[mgsolakis]

I think I removed that pin.

 

[southkogs]

The pin on the outboard is gone (so you're trimmed WAY in) ... the boat is slightly (not a big deal) underpowered ... and you're porpoising? Sumthin's way funky ... post some photos up. You should be plowing (if anything) even with the battery and tank in the back.

 

[JimS123]

The pin on the outboard is gone (so you're trimmed WAY in) ... the boat is slightly (not a big deal) underpowered ... and you're porpoising? Sumthin's way funky ... post some photos up. You should be plowing (if anything) even with the battery and tank in the back.

Yeah. Obviously someone along the way removed the pin because the problem was real bad.

You got a hull problem. Don't just look at it and say its OK....put a steel straight edge on it.

My previous $25 suggestion may not be enough with no pin involved. A smaticus may work, but spending $120 may be more than its worth.

 

[jkust]

Your prop can have an effect on porpoising as well. As for Trim Tabs or Smart Tabs, I've never heard a negative thing about them. Some hulls unfortunatly are natural born porpoisers without some assistance.