1969 hydrodyne 18 speed

The other issue I cannot seem to figure out right off the bat is the speed barrier. The boat rides and handles like a dream up to 26 miles an hour. I have a 1987 Yamaha 2 stroke 150hp V6 which runs great and has plenty of power to pull my skiers.

From 26 to 33 miles an hour the boat is hard to steer, thanks to the manual steering, and the tendency to plow if the motor is not raised slightly.

Over 33 is the barrier, I might get a short burst, but the bow will dive in and down to one side or the other and scrub off speed. This process is not a comfortable one for the driver as it feels uncontrolled. I do not think it has something to do with the new bow tank as it makes no difference if the tank is full or empty. One's natural inclination is it lift the motor to get the bow up, I do this until the prop sucks air to no avail. The rpm's on the motor are at about 4200 so she has plenty left. I'd like to go faster to pull barefoot and unlock the mystery.

Ideas?

Thanks,

Stan

 

Sounds like you might need to:

A) Raise the motor
B) adjust the trim tab above the prop to counter act the steering torque.
C) Install better steering

Dynes have no lifting strakes to they are subject to some abnormal behavior as a result of engine height, the direction the prop turns, cupping/lifting aspects of the prop and loose steering.

 

Run a string down the keel on the outside and see if is straight. It sounds like you might have a hook in the bottom.

jim

 

Jim,

I was thinking the same thing, with his description of the bow twisting one way or the other and then plowing.

Bob

 

In the other thread he said it is flexing. This will make the handling un-predictable.

And, it is very hard on the hull.

jim

 

Sorry, to hear about your issues. It is hard to see what exactly was done. I see some foam and what looks to be the right kind of balsa. When I ripped out my balsa core, there was two layers of balsa sandwiched between three layers of fibreglass made of roving. The balsa in your picture appears very clear, I think it should be covered in roving or at least fibreglass. As mentioned, everything needs to bond to everything to provide strength. The balsa or the fibreglass will not work together if not bonded, that would cause flexing, and as mentioned, eventually a crack. You could install stringers and a subfloor? It is hard to tell though from just one pic, exaclty what you have going one.

Chad

 

One more thought. My boat handled like a beat up old Impala with flat tires and a bas suspension. Once I redid the hull and made it more solid, it handles so much better. Perhaps, solidifying the hull some how for you will help with your performance.

Chad

 

In the original construction of the boat the end grain balsa is dipped in resin and set into the hull. This bonds it to the outer hull. It is then glassed over forming a very rigid glass/balsa/glass sandwich construction. Many new high end boats are still built this way because it is very strong.

The only way that I can see that the boat can flex is if there is no bond between the core and the hull and/or it is not sandwiched.

My hull is so rigid that it transmits every vibration of the motor to the seat of my pants.

jim

 

Must Skis Motors has excellent and cheap suggestions.

Stringers in a Hydrodyne were used to support the floor and nothing else so adding stringers would likely be a waste of time.

Reinforcing the hull will be expensive or very time consuming.

If the hull is twisted fixing it may not be possible. If it is twisting during use it will be hard to measure but it can be "fixed".

"Hook" usually is associated with the bottom not being flat. "Hook" will tend to keep the nose down or up. "Hook" is typically checked with a straight edge against the hull bottom. 1/8" is a lot of hook.

Good Luck!

 

I HAD THE SAME PROBLEM TO A "T" WITH MY DYNE ,SPEND THE MONEY AND TAKE THE TIME TO TAKE THE DECK OFF RIP OUT THT THE FLOOR REPLACE STRINGERS TRANSOM AND PUT A NEW FLOOR IN, I ALSO DID A FIBER GLASS FLOOR COATING SO EASY TO JUST WASH OUT. IT IMPROVED PERFORMANCE BY 100 FOLD AND WILL NOW DO 62 MPH WITH THE SAME 175 MERC. THAT I COULD BARELY GET 34 MPH OUT OF WITH OUT WORRYING ABOUT IT DOING A NOSE DIVE.