1984 Thundercraft Tri Hual

[Colroado Boater]

Good Morning,

I have a 1984 Thundercraft Tir Hual w/50HP Evenrude. Someone stole my prop and I am having a hard time getting the right one back for it. With the old prop the boat ran around 33MPH at WOT. I tried putting on what i thought was the right prop a 12x13 Pitch and the motor seamed to reave really high and i could only run 20MPH. Does any one know what size Prop i need to run on this boat. I am tired of buying and returning props. THe next one i buy will be a 17 pitch.

Need your help

 

[steelespike]

Re: 1984 Thundercraft Tri Hual

Without a tac reading its impossible to figure correctly what ypou need.
A 17 is probably in the ball park.It is bad for performance,and motor health to guess on the prop.

 

[Colroado Boater]

Re: 1984 Thundercraft Tri Hual

Thank You Steelespike for your response. But i have no means of putting a tach on the boat. I don't know if they even make a tach that will work whit this engine. I will just go with my gut and get a 17p and hope it works.

Again thanks you for your help

 

[steelespike]

Re: 1984 Thundercraft Tri Hual

Thank You Steelespike for your response. But i have no means of putting a tach on the boat. I don't know if they even make a tach that will work whit this engine. I will just go with my gut and get a 17p and hope it works.

Again thanks you for your help

Tiny tach makes tachs that will work on almost any motor.Reasonable,easy to install, one for your motor will work on any 2 cyl 2 stroke without regard o stator poles.

 

[Colroado Boater]

Re: 1984 Thundercraft Tri Hual

Well It has been a while since I have been on here. I got a 17P prop and it seams to work fine. Lost about 1 mph from the factory prop, but i have a question about my motor. since I put the prop on the moter it gets on plan faster, but seams to be slipping. After getting on plan i drop the thorttle back a little and the moter seam to get a better lug on it. Its like it catches better water or something. I changed the gear oil on it, could not find lower unit oil, talked to a boat mech, told me to use 80-90w gear oil? could this be the prob? Also just wounder if the thin air here in colorado has something to do with it.

 

[steelespike]

Re: 1984 Thundercraft Tri Hual

Not likely the gearcase lube.Is it a new prop and what brand?
If you are running at a higher altitude you may need to rejet.
Its possible the motor is happier throttled back at that altitude.
I have experienced a slight venting problem on my pontoon.It still pushes
but slightly venting usually if I throttle back it will bite and allow full throttle again.Usually if a planing boat at speed starts to vent its total requiring a major speed reduction.

 

[Colroado Boater]

Re: 1984 Thundercraft Tri Hual

Hey Sir

Here is the Prop I bought

SKU:#2311-120-17
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 12?
Pitch: 17?
Blades: 3
Rotation: Standard (Clockwise)

The carbs on this motor has 0 adjustments? I haven't tried re-jetting, don't even know if i could buy new jets for this motor. the boat came from Virginia and ran perfect down there. Before someone stole the prop off my boat it ran alright, and didn't have the issue i am having now!

I am thinking that i just have to be happy with what i have..lol.

Thank you for all the help