outboard hight?

[lok]

from what I read online I am guessing that my outboard is mounted too low......... would raising it 2" or so help out with the performance that much?


Thanks

[PerchBuster]

What HP outboard are you running there? Smaller outboards on tinners etc with limited top end speeds wouldn't matter too much to be honest. Mid to higher range HP it does make a lot of difference though. Generally speaking the cavitation plate should be level with the bottom of the transom for optimal performance at higher speeds and for getting up on plane

[fluxcore]

It's my understanding that being a little low helps out a heavier boat get on plane and the more u lift it the better top end u get (less drag)

[Walleyedude]

It is too low in my opinion.

I wouldn't be afraid to raise it 2" and give it a try. It might even need 3" depending on your HP, application and what you're looking for in terms of performance. Too high and you start to create different handling problems.

[lok]

thanks guys, its a 30hp on a lund ssv 450 pounds or so top end speed around 29mph. I do find running solo that the boat porpoises a little bit. Read that this might help it out.

I pretty much use the main to run from the boat launch to the fishing areas and use the kicker for trolling so my main concern is speed.......

[Walleyedude]

Originally Posted by lok

thanks guys, its a 30hp on a lund ssv 450 pounds or so top end speed around 29mph. I do find running solo that the boat porpoises a little bit. Read that this might help it out.

I pretty much use the main to run from the boat launch to the fishing areas and use the kicker for trolling so my main concern is speed.......

I wouldn't go more than 2" in that case.

The good thing is it's a simple process to lower it back down if you don't like the results.

[KegRiver]

I bought a boat a couple of years ago, because it was small and cheep, perfect for one guy on the local lakes.

It came with a 35 hp Johnson long leg outboard. It ran fine and with just me in the boat it seemed okay. Then I took a co-worker fishing and couldn't get it to plane out.

I checked the draft and found the anti cavitation fin was six inches below the hull so I lifted it as far as it would go, two inches.

Now it will plane out with three guys on board.

Too deep can make a huge difference.

As near as I can find, the ideal all around setting is to have the anti cavitation plane about half an inch below the bottom of the hull.

Above that you will pick up speed at the cost of maybe having issues with cavitation during high speed maneuvers. Below that you loose top end speed and maybe have issues getting on plane.

[KegRiver]

Originally Posted by lok

thanks guys, its a 30hp on a lund ssv 450 pounds or so top end speed around 29mph. I do find running solo that the boat porpoises a little bit. Read that this might help it out.

I pretty much use the main to run from the boat launch to the fishing areas and use the kicker for trolling so my main concern is speed.......

Porpoising is a function of trim, not cavitaion plane depth.
You probably have it trimmed with the bow too high. Or have too much weight in the back. Either way, trimming the bow down a touch should cure it.

[PerchBuster]

If you're getting 29 mph already from a 30 hp that's about max speed already I would say.might gain a couple more mph raising it but not too much.

[ROA]

A 30 and a kicker on the back of an ssv (16. Foot?) is probably to much weight and that is where your proposing problems are coming from. Lift the motor and trim all the way down if you want. I would put all weight up front including getting a longer fuel line and put the fuel tank up there too

[catnthehat]

Originally Posted by ROA

A 30 and a kicker on the back of an ssv (16. Foot?) is probably to much weight and that is where your proposing problems are coming from. Lift the motor and trim all the way down if you want. I would put all weight up front including getting a longer fuel line and put the fuel tank up there too

Yup, most of my outboards used t run needed weight up front.
Putting the anchor and tank up in the bow fixed it most times.
As far s the pic goes, a, raise that motor up!
Cat

[Walleyedude]

Originally Posted by KegRiver

Porpoising is a function of trim, not cavitaion plane depth.

Motor (cavitation) plate height can actually be a major factor in causing porpoising. Mounting the motor too low will definitely cause porpoising, and often it can't be cured using trim alone.

[EZM]

Originally Posted by Walleyedude

Motor (cavitation) plate height can actually be a major factor in causing porpoising. Mounting the motor too low will definitely cause porpoising, and often it can't be cured using trim alone.

100% agree - One of the primary causes of proposing is not weight distribution - it's set up. Putting more weight in the front of the boat is treating the symptom and not the disease.

I would agree with most guys on here - I'd lift that motor up and line up the cav. plate at to the bottom of the hull or just a tough higher.

For most "fishing" boats - you kind of don't want it too high as you loose a little boat control and suffer a little in the big chop if you are too high and the prop cavitates (breaks the surface and sucks in air) which isn't great for the spline, motor, etc...

[catnthehat]

Originally Posted by EZM

100% agree - One of the primary causes of proposing is not weight distribution - it's set up. Putting more weight in the front of the boat is treating the symptom and not the disease.

I would agree with most guys on here - I'd lift that motor up and line up the cav. plate at to the bottom of the hull or just a tough higher.

For most "fishing" boats - you kind of don't want it too high as you loose a little boat control and suffer a little in the big chop if you are too high and the prop cavitates (breaks the surface and sucks in air) which isn't great for the spline, motor, etc...

Even when my motors were set up perfectly the hull, they still porpoised if was alone because of the boat trim.
Cat

[KegRiver]

Originally Posted by catnthehat

Even when my motors were set up perfectly the hull, they still porpoised if was alone because of the boat trim.
Cat

Funny how that works.

It's not the first time I've been told that a flat tire was caused by an empty fuel tank.

[lok]

thanks for the info guys. I will be lifting the motor up tomorrow and will let you guys know how it works out.


Yes, I know I am pretty heavy in the rear with the kicker so I am careful with loading as much gear up front as I can.


https://www.youtube.com/watch?v=gKIy...ature=youtu.be

[EZM]

Originally Posted by catnthehat

Even when my motors were set up perfectly the hull, they still porpoised if was alone because of the boat trim.
Cat

Originally Posted by KegRiver

Funny how that works.

It's not the first time I've been told that a flat tire was caused by an empty fuel tank.

Ok - lol - you boys have had your poke of fun ..... I don't think anybody mentioned "absolutes" in this thread. Every situation is different - some are common.

A light boat with too much weight in the back will, quite often, cause some issues - but if the boat was set up with, maybe a jack plate, or set to an appropriate depth, and/or trimmed properly, etc.. etc.. that is far less likely to happen - that was my point.

Adding weight to the front is addressing a symptom.

Setting the boat up addresses the root cause (the disease).

Sometimes you can cure the disease and other times you can only make it a little better.

I've also been told by a few guys that their boats were "set up perfectly" YET, ironically, despite their self proclaimed engineering expertise, I was able to fix their problems with a small piece of square tubing (changing the trim angle and cav height) in 10 minutes.

Now - I gotta run ....... there is a sale on headlight fluid and I gotta get over to the local canadian tire before the limited supplies run out.

[Walleyedude]

Operating a boat with a hydraulic jack plate is a good way to experience first hand the drastic affect that motor height has on porpoising. It's the first thing I'd check when trying to cure a porpoising issue, because getting the motor height correct will improve performance.

Weight distribution is important as well, and it's a low cost way to address the problem. However, simply weighing down the bow of the boat often hurts performance and handling, especially on higher performance boats where bow lift is critical. Getting as much hull out of the water as possible is the key to speed, and every HP used to lift the bow is one that's not being used to push the boat forward.

Porpoising is a harmonic bounce caused by two factors. The drag of the motor vs the lift of the hull, and the ability of the motor to hold the bow up under power. Both are affected by weight distribution and power to weight ratio, but the root causes are engine mounting height and propeller design.

Get your motor height set correctly, prop your boat correctly, and weight distribution should be the final piece of the puzzle to get it perfectly dialled in.

[Walleyedude]

Originally Posted by Jet

The idea is to have the motor set to a height so that the range of trim can be set to accommodate the boat loading conditions.

Fastest speed is going to be with trim up to the point that it just nearly starts porpoising. That point will require more up trim when the boat is heavily loaded at the front, and more down trim when lightly loaded with most of the weight at the back.

If you can't achieve that point at all passenger / weight loading conditions you're operating through, then likely the motor is at the incorrect height. And if you can't reach porpoising, you're plowing at the bow and that will effect speed.

On my boat, trimming up a bit from fully down at all speeds/loads/passengers, results in about a 7-8kph speed increase. I need more up trim when I have 2 passengers and gear in the front. Also, RPM goes up when I do that because there's less load on the motor.

At cruising speeds I agree, trim angle is a constant compromise between maximum speed/efficiency and ride/handling (porpoising).

On a properly setup boat at WOT though, excessive trim should not cause porpoising. The prop should simply start to cavitate and lose speed, creating a rooster tail. If you have a porpoising issue at WOT, you have a motor height issue or a propeller selection issue.

[catnthehat]

Originally Posted by EZM

Ok - lol - you boys have had your poke of fun ..... I don't think anybody mentioned "absolutes" in this thread. Every situation is different - some are common.

A light boat with too much weight in the back will, quite often, cause some issues - but if the boat was set up with, maybe a jack plate, or set to an appropriate depth, and/or trimmed properly, etc.. etc.. that is far less likely to happen - that was my point.

Adding weight to the front is addressing a symptom.

Setting the boat up addresses the root cause (the disease).

Sometimes you can cure the disease and other times you can only make it a little better.

I've also been told by a few guys that their boats were "set up perfectly" YET, ironically, despite their self proclaimed engineering expertise, I was able to fix their problems with a small piece of square tubing (changing the trim angle and cav height) in 10 minutes.

Now - I gotta run ....... there is a sale on headlight fluid and I gotta get over to the local canadian tire before the limited supplies run out.

I wasn't joking , was dead serious.
Motor set perfectly on a 14'car topper or Jon style and you can adjust the motor trim all you want , you are still going to have to put some weight up front if you are alone .
ig load a 18 footer and unless you adjust your boat trim you are still going to have issues with man boats.
My 16' Tri hull Glascon bounced like nobody's business unless I had weight up front until I put on a Hydrafoil,and that was with a 70HP Johnson, recommended horse power for it.
Boat was set up at the factory.
Cat

[ROA]

Having the top up acting like a big old sail on that little ssv shure ain't helping things either. She must be a handful in the wind and waves when up on step!

[lok]

Originally Posted by ROA

Having the top up acting like a big old sail on that little ssv shure ain't helping things either. She must be a handful in the wind and waves when up on step!

Don't notice a difference with the bimini at all. I thought it would catch a lot of wind but not enough to notice, even when trolling with the kicker.

Got the motor moved up and am glad I did as the motor was never mounted with bolts from the dealer. So just waiting for the 4200 to cure and I`ll take it out and test it. Brought it up by 2"








OLD

[EZM]

Originally Posted by catnthehat

I wasn't joking , was dead serious.
Motor set perfectly on a 14'car topper or Jon style and you can adjust the motor trim all you want , you are still going to have to put some weight up front if you are alone .
ig load a 18 footer and unless you adjust your boat trim you are still going to have issues with man boats.
My 16' Tri hull Glascon bounced like nobody's business unless I had weight up front until I put on a Hydrafoil,and that was with a 70HP Johnson, recommended horse power for it.
Boat was set up at the factory.
Cat

Listen - for sure - if you have a super small light boat (or boat which displaces a large amount of water compared to weight) and you have all the weight in the back - you are going to have some handling issues in many (most issues).

My point was probably the same as what you are saying - Trimming up changes the angle of the prop/cav plate in relation to the angle the gull is cutting through the water. Raising or lowering the cav plate, while at a neutral 90 degree position is something completely different.

One addresses the proper set up (the height) and the other "tunes" the boat which is trim.

Trim alone won't correct the issue. I don't disagree. But lifting or lowering the leg has a much better result. I've set tinners up over 2" high (and some 2" low) to correct various handling issues.

[lok]

had a chance to test the boat out yesterday solo with gear and with two of us with gear and the boat is handling a lot better.

It gets up on step in about two boat lengths compared to 4-5. Also the bow does not rise as high when taking off. Top end speed has gone up 1mph, and I am able to trim up the motor now without the boat porpoising right away.

The only thing I am not sure of now is I am getting spray off of the first deflector plate. Not sure if this is normal as the deflector plate use to be at water level when on step at the original mounting height....