Quick help-prop!!

[travis g]

i have a 1860 jon w/ 115 yamaha inshore. i have been told i need a 16p stainless. so....13.5 or 14.25 diameter? found one of each but id rather not just throw part darts.

 

[81_chapparel194]

Re: Quick help-prop!!

aye what was on it?

 

[travis g]

Re: Quick help-prop!!

4 blade ss 18p. Dont like it at all

 

[jestor68]

Re: Quick help-prop!!

What WOT rpm are you getting with the 4 blade?

Generally, putting a 3 blade of like pitch on it will raise rpm a little and gain speed.

 

[travis g]

Re: Quick help-prop!!

4800

 

[travis g]

Re: Quick help-prop!!

Need to be at 5600-5800 don't I?

 

[mpsyamaha]

Re: Quick help-prop!!

I would go for the 13.5" diameter prop, and 16p will bring the rpms up some. You may even end up going with a 15p.

 

[steelespike]

Re: Quick help-prop!!

To evaluate your setup we really need more info.Year of motor,prop size,gear ratio,wot rpm and speed.
A description of why you don't like it.Is the boat a bare 1860?

 

[travis g]

Re: Quick help-prop!!

97 115yam inshore. Have a 4bl 18p now. When the boat is loaded it doesn't have enough power to jump out of the water. It stalls back. Only get about 4800 wot

 

[steelespike]

Re: Quick help-prop!!

I think you may have more issues than a prop. To gain 1000 rpm would take about a 5" reduction in pitch.
Putting you at about 13", thats pontoon boat size.What is your all up weight?
I've seen tests of 23 ft boats 3000 lbs all up weight running a 17" prop at 6050 rpm 40.7,3.94 seconds to plane.
A 17ft8" Skeeter at 2422 all up with a 19" prop turning 5500 @ 46.7,3.60 to plane. Granted a faster bottom than yours.
17'6" Stratos 2600 lbs all up,21"prop. 5450 @49.7 Again a faster bottom than yours. But I think you can see
unless you have a really heavy load your 18" should get it done.

 

[travis g]

Re: Quick help-prop!!

Very heavy. 20gal fuel. 6-8 grown men and gear. That's when it chokes out. Main issue is rpm with just me and a half tank. Doesn't turn enough. 0-45mph in a blink but only getn 4900 or so. Trimmed all the way 5000

 

[Silvertip]

Re: Quick help-prop!!

4800

That's why you don't like the prop. Way to much prop apparently, but, on a 115 that should be at least in the ball park. I suspect you have an engine/setup/boat issue rather than a prop issue. Without speed at WOT (GPS preferable) it's hard to predict what you need. But at 12% slip your existing setup should yield 36 MPH. Don't spend money on props until you investigate setup and engine performance (e.g., a good tune-up). Check the position of the AV plate in relation to the bottom of the hull. Set the engine to the plate is at least flush to 1-inch above the keel.

 

[travis g]

Re: Quick help-prop!!

Cavatation plate is perfect, carbs and fuel pump have been rebuilt. All electronics have been tested. All systems go. According to my cert mechanic and the seaark/yamaha dealer I need a 16p prop. The 4bl 18p according to them is just too much to turn. I just wondered if I needed 13.5 or 14.25 diameter. I called the dealer back and they said 13.5 is how they set them up and should put me in the 5500-5600 range.

 

[Mi duckdown]

Re: Quick help-prop!!

1. is the dealer going to back up his claim.
2. You mentioned 6-8 full grown men and gear. Is that boat rated for all that weight? just throwing that up.

 

[travis g]

Re: Quick help-prop!!

Rates for 10 or 1150lb. They rig them every day so.....

 

[steelespike]

Re: Quick help-prop!!

Very heavy. 20gal fuel. 6-8 grown men and gear. That's when it chokes out. Main issue is rpm with just me and a half tank. Doesn't turn enough. 0-45mph in a blink but only getn 4900 or so. Trimmed all the way 5000

What does this boat weigh with just you?Its hard to believe its over 3000 lbs with just you aboard.?

 

[steelespike]

Re: Quick help-prop!!

Very heavy. 20gal fuel. 6-8 grown men and gear. That's when it chokes out. Main issue is rpm with just me and a half tank. Doesn't turn enough. 0-45mph in a blink but only getn 4900 or so. Trimmed all the way 5000

What does this boat weigh with just you?Its hard to believe its over 3000 lbs with just you aboard.?
The prop calculator says you can't go 45 at 5000 rpm with a 18" pitch. that would require negative slip.
Something is in error.

 

[steelespike]

Re: Quick help-prop!!

Very heavy. 20gal fuel. 6-8 grown men and gear. That's when it chokes out. M

 

[steelespike]

Re: Quick help-prop!!

Very heavy. 20gal fuel. 6-8 grown men and gear. That's when it chokes out. Main issue is rpm with just me and a half tank. Doesn't turn enough. 0-45mph in a blink but only getn 4900 or so. Trimmed all the way 5000

What does this boat weigh with just you?Its hard to believe its over 3000 lbs with just you aboard.?
The prop calculator says you can't go 45 at 5000 rpm with a 18" pitch. that would require impossible negative slip.If we use 45,2.00 ratio,18" pitch,more reasonable 10% slip we get 5867 rpm
If we use 5000 rpm,2.00 ratio,18" pitch,10% slip we get 38.4 mph.As far as I know the 115 2 stroke has 2.00 gear ratio.
Some portion of the info is wrong.

 

[travis g]

Re: Quick help-prop!!

Dunno what it weighs. It's a 18' jonboat. Had some tach issues and just installed a new one. Will know the real deal Saturday or Sunday. I don't see how that motor could possibly turn a four vlade 18 at 5700 though but.....