Prop Question - 1988 70 HP Evinrude

[Gryphon]

Parents have a 17' Aluiminum Sylvan bowrider with a 1988 +/- 70 HP 2 stroke Evinrude on it. It is able to get my brothers out of the water on a wakeboard who weigh in the 200 lbs range but could use a slightly better hole shot if thats possible. Just wondering what my best option would be for this engine for a better hole shot and would be willing to sacrafice speed.

Thanks

 

[HighTrim]

Re: Prop Question - 1988 70 HP Evinrude

Welcome to iboats Gryphon.

What is the boats current WOT RPM?

 

[Gryphon]

Re: Prop Question - 1988 70 HP Evinrude

I asked Dad that before posting but neither one of us has paid any attention to that. I will make sure to look next time but the engine is being serviced tomorrow morning and I was going to get a new prop if the one we have is not sufficent.

Thanks for the welcome, hope to get my own new boat in the next year or two after learning on this one.

BTW I see we are both from Hamilton.

 

[guy74]

Re: Prop Question - 1988 70 HP Evinrude

What pitch prop does it have on it now? I run a 15" pitch prop on my 1988 60hp, we even ski behind it. Also might want to port the prop for a better holeshot. There are a few more tricks to get more pulling power out of a smaller motor, just depends on what sacrifices you want to make.

 

[Gryphon]

Re: Prop Question - 1988 70 HP Evinrude

I guess I would like a bigger hole shot, would sacrifice top end speed. What are the other options to sacrifice?

So I am looking for size dimensions etc for a ski/wakeboard only prop for this setup.

Thanks

 

[guy74]

Re: Prop Question - 1988 70 HP Evinrude

All I can say is on my 15.5 ft trihull, we run a ported 13.75 X 15 Hustler prop. I have the ports drilled out to 5/16 dia. I have also found that a Se sport hydro foil really helps direct the prop thrust down and relly makes the boat pull well when pulling up a skiier. My boat weighs around 2000lbs including motor, fuel, battery, and passengers ect. I also have used a 14 X13 hustler prop, but it cut the top speed down to 28mph @ 6200rpms, the 13.75 X 15 runs 34 mph @ 5950rpms.

 

[HighTrim]

Re: Prop Question - 1988 70 HP Evinrude

Well welcome fellow Hamiltonian.

If you ever need any help with her, let me know.

Good luck.

 

[Gryphon]

Re: Prop Question - 1988 70 HP Evinrude

So a 13.75 X 15 is expected to work well on this engine? How many RPM should the engine be running at?

What thread is best for learning about size, pitch etc and the relation to performance?

Thanks

 

[Gryphon]

Re: Prop Question - 1988 70 HP Evinrude

TTT

Anyone?

 

[199675hpforce]

easy dude

easy dude

if you have replaced the fuel pump diaphram with new,cleaned out with powertune. Drop to 12 pitch or 11.5 you will be cruising 27-33mph if its anything like my 17ft alum starcraft fishmaster 75hp force outboard. You might see better speed than me ive got lots heavy equipment. Drop that prop down. Im running 4600rpm all out i also have a couple other props i bought 10.50 maybe little high 11.

 

[bassman_n]

Re: Prop Question - 1988 70 HP Evinrude

Chances are that the prop on the boat is the standard 13 1/4 x 17 OMC prop that was probably sold with the boat. Dropping to a 15 pitch will help hole shot. Your not giving us much to go on without speed and rpm stats. I'm usually not a big fan of Ballistic propellers but on curtain types of boats they can do amazing things. On other boats like yours I've seen a up to a 4 mph increase and 200-400 rpm increase when comparing the 13 1/4 x 17 OMC aluminum to the 13 1/2 x 17 Ballistic. Hole shot is improved especially when the prop is drilled to allow some exhaust gases to run over the blades during hole shot. Cornering is drastically enhanced but you will find that with almost any stainless prop. Hope this helps some.