Yet another prop question.

[legacycycles]

Ive got a 20ft vision bass boat that has a zuki dt 115. I know its underpwerd but anyway. It has a 12x17 alum prop on it now,and has a very slow holeshot. Top end the engine will turn about 4200rpms or so.
Now by looking at props the 12x17 is the highest number pitch avaliable. From here they go to 14inch props and all the way to an 10 or 11 pitch. I understand the 1 pitch down 2oo rpm up,as well as holeshot vs top end. However if an engine is only turning 4k then it gets repropped to turn say 6k It seems to me that top end would remaine the same if not more due to the engine speed. Just my thoughts. How about yall?
If i keep the boat ill be looking at increasing engine size so none of this really matters just thought id get a little discussion going.

 

[sublauxation]

Re: Yet another prop question.

More revs but displacing less water per turn?

 

[legacycycles]

Re: Yet another prop question.

I understand displacing less water but it seems to me it might would balance out with increased engine revs and prop diameter.

 

[rutcutter]

Re: Yet another prop question.

If you look at and study one of the prop calculators you will see that pitch makes more difference in top speed than RPM does. It seems to me that if you look at what your max RPM should be for your motor and put the proper pitch prop on it to achieve the recommended RPM then your problem would fix itself.

 

[Robbabob]

Re: Yet another prop question.

If you look at and study one of the prop calculators you will see that pitch makes more difference in top speed than RPM does. It seems to me that if you look at what your max RPM should be for your motor and put the proper pitch prop on it to achieve the recommended RPM then your problem would fix itself.

+1

Also, you already realize your HP is down and you are going to take care of that. HP to match the weight, yeah, that's the ticket!

A few hundred now for the right prop, then maybe your current 17P prop will be right with the higher HP in the future.

Good luck!

 

[legacycycles]

Re: Yet another prop question.

i was just wondering,and figured it might make for some interesting conversation.
If i do keep this boat it needs some work done,paint etc,and i will defintley sell the 115 and get a 200 for it so i really dont have any plans to try another prop but then agin you never can tell with me,lol..I had orginnally bought this as a project and decided to sell it due to time and room issues,but now i may keep it. Its kinda growing on me.
By the way does anybody know much about vision bass boats,other than they went outta buisiness in 94.

 

[steelespike]

Re: Yet another prop question.

Didn't have the year of the motor but it appears props are available up to 24" for a 94 motor. As I understand it a bass boat is built for speed.
My very limited research; 94 20' weighs about 1200. It appears a 115 should be respectable on that. and probably run a 16 or 17" pitch.
I think something more than prop selection is going on. What is present max speed.
Combo should run around 40 and the motor is rated for 5,750 rpm.

 

[legacycycles]

Re: Yet another prop question.

Didn't have the year of the motor but it appears props are available up to 24" for a 94 motor. As I understand it a bass boat is built for speed.
My very limited research; 94 20' weighs about 1200. It appears a 115 should be respectable on that. and probably run a 16 or 17" pitch.
I think something more than prop selection is going on. What is present max speed.
Combo should run around 40 and the motor is rated for 5,750 rpm.

You are correct. the boat weight is 1200dry. Max hp for the boat is 235hp.
The engine on it now is a 93 dt115 zuki. Max rpm at wot is about 42-4300rpm. rpms will come up if i continue to trim the prop up out the water but then it loses bite obviousley. Also the holeshot is extremley slow. Once it planes it does fine but agin it takes it 2long to plane. Top is guessing but id say 30-40,probably closer 35mph. I forgot mu gps when i went out.
I too thought the 115 would do ok but me being me i want more. Just the way i am.

 

[steelespike]

Re: Yet another prop question.

The max rating at 235 does make the 115 look even smaller ,rule of thumb it should be about 3/4 of rated hp. At 4,300 you would need to drop about 7" to get 5,700
that's really extreme 10" is for difficult loads like a pontoon.I think you should varify the tach is accurate,the throttle opens all the way motor is in excellent tune, bottom clean and smooth,antivent plate(just above the prop)should be about even with the bottom or a little higher.

 

[legacycycles]

Re: Yet another prop question.

The max rating at 235 does make the 115 look even smaller ,rule of thumb it should be about 3/4 of rated hp. At 4,300 you would need to drop about 7" to get 5,700
that's really extreme 10" is for difficult loads like a pontoon.I think you should varify the tach is accurate,the throttle opens all the way motor is in excellent tune, bottom clean and smooth,antivent plate(just above the prop)should be about even with the bottom or a little higher.

Everything youve described ive allready done with the exception of verifying tach reading. The boat idles fine and the tach is reading about 1k.It does seem be correct but i have not checked it agint another one.
The throlltle was only opening maybe 3/4 of the way but the engine wouldnt even plane the boat then. I cleaned the carbs fixed the throttle issue and thats where iam now. I feel pretty certian its a prop issue just because the way it acts when running. I was looking at a 14x12 as oppesed to the 13x17 thats on it now,but like i said i dont plan on keeping this engine on the boat.

 

[steelespike]

Re: Yet another prop question.

A 5" pitch change is good for about 1,000 rpm the large increase in diameter
will likely lower that some. Being short 1400 rpm makes me think your still lacking
full power.Have you done a compression check sure about timing, proper carb sync?
If it is a 4 cylinder you might just be short a cylinder.You wouldn't be the first to not realize you are missing a cylinder on a 2 stroke.Sometimes folks don't notice on a 2 cylinder except for the loss of power.

 

[legacycycles]

Re: Yet another prop question.

A 5" pitch change is good for about 1,000 rpm the large increase in diameter
will likely lower that some. Being short 1400 rpm makes me think your still lacking
full power.Have you done a compression check sure about timing, proper carb sync?
If it is a 4 cylinder you might just be short a cylinder.You wouldn't be the first to not realize you are missing a cylinder on a 2 stroke.Sometimes folks don't notice on a 2 cylinder except for the loss of power.

I pretty sure the engine is ok. I am a mechanic and thats the first thing i check is engine condition. Comp. is good with 125 the lowest 130 the highest. And shes hittin on all four. Ive cleaned and syncd the carbs but thats aboyt it. I may actually keep this engine and swap boats for a 79 glastron and stick the 115 on it . May go look at it tomorrow,who knows? Right now ive got everything for sale cause i really dont have the time or the room right now. Allways hustling for a buck.lol.