uncontrollable tinnie

[gmill75]

hey new to boating - just bought a 4 m tinnie with 40hp tiller steer suzuki. when i got it had a foil on. made it easy to get up on the plane - hassle free - but when at speed it would regularly dig in and bank sharply to the right. very scarey for novice. messed around with the trim and took foil off. still every now and then same is still happening and its a bugger. have had a few good runs when i had another adult in boat, and adjusted the weight distribution. is it just a case of working out a good balance of weight across the whole boat, or are there some tips that may set me on the right track. cheers geoff

[Poodroo]

Perhaps the cav plate is situated too low maybe? Not sure. I too had issues with foils on my old tinny with a 25hp Tohatsu. It would dig in unexpectedly and scare the living daylights out of me. Took them off and the problem was solved. Only thing I can think of in your case if the tinny still has the problem is the cav plate is not correctly positioned. Perhaps a photo posted on here could help more.

Poodroo

[gmill75]

cav plate??? what is that - sorry about my lack of knowledge

[finga]

Mate the cav. plate is the big plate near the bottom of the motor but above the propeller.
It would have had the foils mounted to it.
It could be a trim issue but if you take a couple of pictures looking from the back of your boat and from the side looking square onto the motor and the bottom of the boat a better 'guess' can be made.
Bugger it...just bung lots of pictures of your pride and joy for all to see.

[Blackened]

G'day

Anti-Cavitation plate is the flat casting that's directly above the propeller, this should sit on or near the surface of the water whilst planing.

The cav. plate should be inline with the bottom of the hull when trimmed down to normal position.

Remember a 40hp is a fair bit of grunt for a 4m tinnie, so don't be too surprised about dodgy handling with excessive speed

What's your prop like? Damaged? what diameter and pitch? (this is stamped on the outside of the prop or on the internal lip)

Dave

[gmill75]

thanks for info. i went and did a search on what a cav plate was - should have done that beofre asking . sorry . will check where it sits in the morning. must admit sitting on 3/4 throttle i have little hassles - its really only when at full throttle the near death roll comes into play. will definetly drop size of motor once this one dies -its pretty old but still going strong

[mungsta]

Hi Gmill, I have a 4.35m tinnie with a 40 yammie on it, goes like the clappers but i think the motor could be raised approx 30-50 mm to line the cav plate up with transom as it will dig in a bit too especially when in a following sea. I am thinking (or hoping) it will give me a bit more bow up as well.

Cheers
Mungsta

[oldboot]

I'm no expert in these matters but it sounds like its getting too far up on the plane and then falling over.

I gather you are stearing left handed therfore sitting on the right.

cheers

[wags on the water]

Maybe you just have to slow down

[crossy]

lol i had the same problem mate. i went out by myself and just about threw myself outa the boat. its best not to go full speed specialy with a 40hp on a 4m tinny. tillers can be very dangerous getting up that range of hp. like the other fellas said mate try ajusting the trim. i have one setting when im by myself and another for when the wife is in the boat, it make a world of differance.


Yours aye
crossy

[finga]

Maybe you just have to slow down

More often then not truer words have never been said.
Tinnies are only meant to go so fast in perfect conditions.
Faster then that they're accidents waiting to happen.

[Chimo]

Hi GMill75

Agree with the esteemed contributors above, issue seems to be height of motor and lead foot and too much power!

Can I suggest that you never operate this craft without having the kill switch lanyard on your wrist and you (and you passengers) seriously consider the wearing of a floatation device when operating at speed in order to ensure that you can enjoy this site for the long term.

Probably best that keep your phone in a waterproof container too and that you attach all you rods tackle boxes and other stuff with safety lines as there is a strong possibility that you may lose them when you invert the "titanic" (you didn't mention the boats name but we are here to help)

PS Where do you operate? If we all know we can keep an eye out.

Good luck and good on you for asking.

Cheers
Chimo

[gmill75]

thank you all for info. very helpful. no name on my boat but just look for the slow moving tinnie with a big motor on the back on the gold coast broadwater. cheers geoff

[Crocodile]

I suspect that the engine trim is using the furtherest "in" position, this will cause the bow to press down and account for the twitchy handling. At higher speeds most boats need a bit of up trim. Try moving the tilt pin out a hole or two. You will now find that climbing onto the plane will have more bow-rise, make your crew sit forward and then move aft when properly on the plane. Without a method of adjusting the engine trim under way you have to compromise.

[gmill75]

Thank you all for your help. went for a fish today and moved the trim to the third level (basically the middle). got up and on the plane easily, and did not dig in once or turn sharpley. cav plate sits where its supposed to be. i kept it at 3/4 throttle, more than enough to plane with 2 adults and 2 small kids in it, and definitely still pushing along at a nice safe speed. again thank you to all that reponded, really appreciated. cheers geoff