Prop test results

[travis g]

I was awful wrong. With the new tach installed my 4bl 18p is turning 6000wot with 2 people and a full tank. The 16p I Tried was a disaster. Half throttle hit 6k. What would a 19p 3 blade do for me? Wouldnt mind a little more speed but I'm not willing to lose very much hole shot.

 

[Barnacle_Bill]

Re: Prop test results

What motor?

 

[V153]

Re: Prop test results

What boat? How many hp? How fast?

 

[travis g]

Re: Prop test results

1860 mv seaark Jon boat. 115 yamaha.

 

[BonairII]

Re: Prop test results

Probably gonna need to go much larger than 19p if you're redlining at half throttle with a 16p.

 

[travis g]

Re: Prop test results

Thought maybe a 4bl 18 and a 3bl 19 would be close.

 

[Tiderunner88]

Re: Prop test results

Just went from Black Max 19 to the new Spitfire 19 four blade- same rpm @5300- same WOT 40. You could pitch up and try 4 blades, the hole shot is excellent with a 115 merc.

 

[Texasmark]

Re: Prop test results

Unless you are carrying around filled 55 gallon drums, you are way over powered for that boat. I used to rent a 20 footer and run it with my 9.9. Course you can watch the gals on the Alligator show. They have a john of that general size with a 115 on it, as do the guys with the canvas top. On prop pitch change, the number is about 150 rpm per inch down if you increase pitch and up if it's the other way. The 4 blade is usually reserved for high loads aft on heavy boats without a very good planing surfaced hull. Your john is about as good as it gets in terms of easily planed hulls.

But doesn't matter what you buy. What matters is if it works for you or not!

Mark

 

[travis g]

Re: Prop test results

I do carry a lot if weight at times. It was rigged with the large motor by the state. It used to be a fisheries boat for Florida.

 

[sweet addiction]

Re: Prop test results

If hole shot is your main concern then stick with a 4 blade. Are you talking stainless or alum.?

 

[travis g]

Re: Prop test results

Stainless inly

 

[jestor68]

Re: Prop test results

That's because the info you provided initially was wrong. :facepalm:

So you know, your WOT rpm range is 4500-5500 rpm.

Going from 4 blade to 3 blade add one of pitch. So if you are turning 6000 with an 18 4 blade and go to a 19 3 blade, you will likely turn the same rpm(or close to it).

So, what do you need to do to lose 500 rpm and switch to a 3 blade prop?

Rule # 1: one inch of pitch equals 150-200 rpm change.

 

[sweet addiction]

Re: Prop test results

And going from aluminum to stainless in the same brand and prop configuration will loose I think if I am remembering this correctly.......somewhere around 200 rpm.

 

[steelespike]

Re: Prop test results

I still wonder why it won't carry 8 men and plane? What is the actual all up weight.
Your surely not going to solve your weight issue with more pitch.
The boat must be way over its rating with 8 people.
Again my 25hp 18 ft Crestliner tiller bare utility, about 800 lbs rigged, would plane easily with 6 adults
averaging about 150 lbs. Probably about 20 mph.I'm sure your much heavier but at almost 5 times the hp.
I do wonder if your 18" prop is actually an 18?

 

[travis g]

Re: Prop test results

Taking the prop to a prop shop on Nashville. He is going to add cup to the blades. It is stamp m18. He said adding cup will help sow with the rpm. I found a corroded wire form the power pack yesterday. I believe I may be losing power under heavy load due to elec breakdown. It will plane out with a heavy load but it bogs an takes a minute, and its not real consistent.

 

[steelespike]

Re: Prop test results

Adding cup will reduce rpm but it's usually like adding pitch.
The right cup might help hole shot.