Boat not set-up properly

[canadian_fisher]

Just bought a Boat and Motor from a Dealer in NY State.
1993 Monark 1600 Fish and Ski (Aluminum)
1995 Mercury 100HP (w/ SS prop)

Here's what I am concerned about:
- Boat "twists" to the Left dangerously up acceleration.
- Twisting goes away, when trimmed upwards.
- AT WOT, the boat "dances" wildly when trimmed up.
- If trimmed down, I get a lot of Bow-turn that's hard to control.
- Porpoises like CRAZY at most speeds unless trimmed down to keep bow tight.

What I've noticed:
- Skeg looks like a Banana at 1/2" to 3/4" off centre.
- Motor is on 2nd hole set.
- Cavation plate (I believe) is 1" below the boat.
- RPM's were 5200 @ 43MPH (before Hydrofoil installed)

What I've done so far:
- Installed a StingRay Hydrofoil yesterday
- Solved some but not all Porpoising
- Slow down the boat to 40 MPH from 43 MPH
- WOT is only 5000 RPM instead of 5200
- Still drives CRAZY when trimmed-up and very hard to keep in a straight line.
- Still "twists" to the left (even more now) upon acceleration.

Any input / suggestions would be appreciated............

CF

 

[steelespike]

Re: Boat not set-up properly

I think I would start by taking off the foil until you have tried all else to tame the boatI. would start by raising the motor at least to the point the antivent plate is even with the bottom of the boatIn. fact I would raise it until just before ventilation becomes a problemBe. sure that it pumps water properly while doing thisSkeg. could be causing problemsLeaning. to the left (port) is usually caused by propeller torqueThis. might be helped by propeller selection.

 

[steelespike]

Re: Boat not set-up properly

Didnt' mean to post yetYour. motor could be as much as 2 inches too low this might cause all kinds of problems.
Raising it will give you more speed and I think control-Porpoising control.Porpoising may be controlled by careful selectionWhat selection.What te te horsepower rating of boatLet boat?Let us know what you find after raising the motor.

 

[canadian_fisher]

Re: Boat not set-up properly

Hi Spike.

I'll go home a get a closer look at the level of the cavatation plate WRT the bottom of boat.
HP Rating for Boat is 100HP, as per Coast Guard Label.
Prop is a Quicksilver 21P (but I'll check that too).
Once the Skeg is fixed, that will eliminate one (or more) issues, I hope.

Thanks. CF

 

[canadian_fisher]

Re: Boat not set-up properly

Question:

What typically happens to the boat when the skeg is bent 1/2 to 3/4" like in my case?

Any input is welcome.

CF

 

[tashasdaddy]

Re: Boat not set-up properly

don't try to straighten it yourself, they don't like to be bent. almost have heat, carefully so not to melt the seals in the lower unit. try to adjust the steering tab above the prop to counter the skeg. smart tabs instead of hydrofoil.

 

[steelespike]

Re: Boat not set-up properly

Skeg could cause any number of control problems.
If the motor is the max then the boat will be running at the edge of its design limits so setup will be critical.
Trim tabs are a much better option than a foil after you have got everything set as good as possible.Check into the smart tabs Folks seem to be having great results with them.

 

[canadian_fisher]

Re: Boat not set-up properly

The cavatation plate on my Merc 100 is about even to the bottom of the boat when trimmed up square. The skeg looks pretty ugly, so its going in for a tune-up.

I agree that "Smart Tabs" might be a better solution, but I use this boat for fishing as much as towing a tube.
Maybe I'll get the Trolling Smart Tabs, that help slow the boat down too.

Also, I sent a line directly to StingRay to see what they think. I am curious to their response to the problem.
I need to get rid of this damn porpoising, and wild ride issue soon as possible.

Cheers. CF

 

[steelespike]

Re: Boat not set-up properly

Definately get the skeg fixed then
raise the motor another hole to see what happens.If it will operate there it can only help.
Adjust your trim carefully give it a chance to settle in each position.It may
behave differently going from low to high or high to low.
If you can find a spot that has only a little porpoising simply moving the gas tank or batteryforward a few feet
might solve it.You might check the rear 1/3 of the bottom of the boat with a long straight edge for rocker, convex curve, or hook, concave curve.Generally speaking rocker will cause porpoising hook will tend to cause plowing.My guess is if anything there is a little rocker.
While I have had good luck with foils if I was doing it today it would be something like smart tabs.Definately consult with them before making any decision.

 

[canadian_fisher]

Re: Boat not set-up properly

Alright........ heard back from Stingray rep from their website.
He definately agrees that a bent skeg needs to get repaired or everything will be exagerated as I am seeing.

BTW: With 4 big boys and loading to the ears with camping equipment and coolers........ I had a nice slow "plane" going with Stingray attached....... high speeds is still a different story.

Thanks....... more to follow.

 

[canadian_fisher]

Re: Boat not set-up properly

OK....... fixed skeg last night with a Propane torch, Block of wood, and a Ball-peen hammer. I tried a bunch of ideas from iboats but nothing worked except lots of heat and brute force.

Took off a quarter-size chunk of alloy which we replaced with some sort of Liquid-Metal product. Worked pretty good.

Tonight we are going to play with set-up again;
With / without foil, and different Torque tab settings.
Not so sure about moving that 400lb motor up another hole set...........

More to follow.......... CF

 

[canadian_fisher]

Re: Boat not set-up properly

Test #1........ complete.........
Skeg is now straight, and square to LU.
Hyrdofoil still attached to cavation plate.
Motor still on second hole set.
Boat still porposing (a bit) but better than before Hydrofoil.
Prop will now ventilate before I get the bow up to high, which avoids the Wild-Ride.
Top speed is now only 38 MPH (down from 43 MPH).


Test #2 .......tonight.......
Removing the Stingray Hydrofoil !!!

The saga continues.......... CF

 

[canadian_fisher]

Re: Boat not set-up properly

Test #2 complete.......... removed the Stingray Hydrofoil.

Well what a different.
I managed to get back my 5200 rpms and 42 MPH.
Skeg straightening make a world of difference.

Still porposing but manageable.
100HP gets that boat up on plane in seconds.
Still trolling that 100HP under 5Kph.

Conclusion........ returning the Stingrap, saving $$ for Smart Tabs.

Thanks...... anybody got their 2 cents to add??