Need to replace prop, opinions?

[strosk]

OK guys, I read these forums all the time and now need to ask you experts for an opinion!

I just bought a 1987 16' smokercraft deep V powered by a 1987 Johnson 40 HP VRO. The current prop is badly beaten and need replaced. The current size is 11-3/4x17. I know RPMs at WOT would be a tremendous help, but the boat doesn't have a tach, so I'm leaning on you guys for your best opinion otherwise. I may end up getting a tach before a new prop just to be sure I'm not gonna damage the motor. The boat is a little slow out of the hole, but planes out pretty good and I've been able to get a top speed of 28 mph on GPS. The motor sounds perfect to me, but I'm certainly not an expert.

So, my question is whether I should stick with the same size or decrease diameter or pitch? (I wouldn't think I'd want to increase!)

 

[steelespike]

Re: Need to replace prop, opinions?

I would say your pretty close.You might get your prop repaired and test again
You could get a tiny tach; reasonable,easy to install,and fits any 2 stroke 2 cylinder.Only way to fine tune your setup and be sure your motor operates in its ideal range.Fine tuning Motor height can improve performance at no cost.
Then you can decide if you want to make a prop change and save the old prop for a spare.

 

[Mwp909]

Re: Need to replace prop, opinions?

I would stay with the same size prop, just change to a stainless steal one. It will get you on plane faster and give a little higher top end without increasing your rpm?s. Aluminum props give and flex more under pressure than a stainless prop does

The down side is a stainless prop cost about three times more.

 

[strosk]

Re: Need to replace prop, opinions?

Steelespike, What is the average cost and down time for prop repair? I don't know anyplace close that does it, so I'd probably have to send it in. Also, since the tiny-tach only comes with 6' of cable, I assume these usually mount back near the motor somewhere? I'd like to have a gauge on the dash, but I'm also a little confused as to how it connects. Do you know if my motor has connects for a tach? What do you think about Mwp909's suggestion about a SS prop? Should I really spend the extra money for fishing freshwater PA lakes?

 

[steelespike]

Re: Need to replace prop, opinions?

I believe the wire wraps around a plug wire and is available in a longer length
if requested.Not as slick as a regular tach but effective and can be used on any similar motor.Your motor should be able to have a tach connected but I
don't know its requirements.No doubt a stainless prop could help but without
your present specs its like changing your cars rear end gears without knowing what it has.Idealy you should refine your setup (vertical height) and then with the new specs make a prop selection.With a stainless you may be able to further refine the setup.
You could probably slap a same size stainless on and it would go better but
how much would you be missing?
Prop repair would depend on your location and how busy they are.My guess is about a week.