Wayyyy over propped???

[agarabedian]

Hey everyone I’m struggling. I have a 2006 Wellcraft fisherman 180 center console with an 06 Yamaha f115. It maxes rpm at 4800 and speed is 25. It currently has a 13x19 prop and I’m stuck on what prop to try. It’s a big investment and every “prop calculator” gives me a different answer. I am mainly looking for something that is good all around and won’t make my boat feel underpowered but will get me to the desired 6000 rpm range.
I just serviced the fuel injectors and cleaned all the fuel filters as I originally thought that was it lol. Any help is appreciated!!!

thank you

 

[dingbat]

Hey everyone I’m struggling. I have a 2006 Wellcraft fisherman 180 center console with an 06 Yamaha f115. It maxes rpm at 4800 and speed is 25. It currently has a 13x19 prop and I’m stuck on what prop to try. It’s a big investment and every “prop calculator” gives me a different answer. I am mainly looking for something that is good all around and won’t make my boat feel underpowered but will get me to the desired 6000 rpm range.
I just serviced the fuel injectors and cleaned all the fuel filters as I originally thought that was it lol. Any help is appreciated!!!

Props vary by both size and design. Not unusual to see multiple sizes of different design recommended.

Are you sure your tach is right?

Conventional wisdom would say you have to drop to a 13x13 prop to hit 6000 rpm.

What size prop is the prop selector recommending?

 

[agarabedian]

Props vary by both size and design. Not unusual to see multiple sizes of different design recommended.

Are you sure your tach is right?

Conventional wisdom would say you have to drop to a 13x13 prop to hit 6000 rpm.

What size prop is the prop selector recommending?

West marine is suggesting 13.75 x15 and Yamaha is recommending 13.25x13. I’m leaning more towards Yamaha because it asked my current rpm and pitch. What do you think of a 13.25 x 13?? And Im assuming my tach is correct because it idles around where is should be. Could be wrong but my gps is saying 25 for speed and similar boats with this engine are getting at least 35

 

[Scott Danforth]

im thinking you need to verify your tach and that the motor is running right.

 

[dingbat]

West marine is suggesting 13.75 x15 and Yamaha is recommending 13.25x13. I’m leaning more towards Yamaha because it asked my current rpm and pitch. What do you think of a 13.25 x 13?? And Im assuming my tach is correct because it idles around where is should be. Could be wrong but my gps is saying 25 for speed and similar boats with this engine are getting at least 35

Something isn’t right…going from a 19@4900 rpm to 13@6000 rpm will reduce your top speed even more.

First off… is this a new to you boat?

Have you checked compression?
What is the LU gear ratio? 2.15?
What condition is your current prop? Plugging in your numbers your pushing 40% slip….20% is bad….

 

[agarabedian]

Something isn’t right…going from a 19@4900 rpm to 13@6000 rpm will reduce your top speed even more.

First off… is this a new to you boat?

Have you checked compression?
What is the LU gear ratio? 2.15?
What condition is your current prop? Plugging in your numbers your pushing 40% slip….20% is bad….

Yes this is a new boat to me. Compression is 200 on all cylinders. I just serviced the injectors and changed all fuel filters. As well as changing the spark plugs. Current prop is a black painted aluminum 13x19 in okay condition, not bent at all but missing the paint of the tips of the blades

 

[Sea Rider]

Is it a new boat out of the store/dealer propped with a 19 pitch, or it's a second hand one which previous owner had propped it that way ?

Happy Boating​

 

[dingbat]

Yes this is a new boat to me. Compression is 200 on all cylinders. I just serviced the injectors and changed all fuel filters. As well as changing the spark plugs. Current prop is a black painted aluminum 13x19 in okay condition, not bent at all but missing the paint of the tips of the blades

PB_WLC_182Fisherman_F115XB_2017-05-17_OCC | Yamaha Outboards

yamahaoutboards.com

 

[Scott Danforth]

Yes this is a new boat to me. Compression is 200 on all cylinders. I just serviced the injectors and changed all fuel filters. As well as changing the spark plugs. Current prop is a black painted aluminum 13x19 in okay condition, not bent at all but missing the paint of the tips of the blades

no way your compression is 200. you would need a diesel engine to have compression that high. check your gauge

 

[dingbat]

no way your compression is 200. you would need a diesel engine to have compression that high. check your gauge

I have no clue but I found a number of sources which list the range of a 4 stroke Yamaha as 180-210 PSI

 

[agarabedian]

So does anyone have a recommendation on a new prop size?? Engine is running perfect and has been well maintained. Been doing research and the 13x19 is commonly overpropped for the f115

 

[dingbat]

So does anyone have a recommendation on a new prop size?? Engine is running perfect and has been well maintained. Been doing research and the 13x19 is commonly overpropped for the f115

Nobody can give you a definitive answer unless they have the exact same boat motor combination.

The max rpm for that motor is 6300. Your currently running 1400 rpm below with ~ 40% slip. Anything would be better at this point

The performance specification I posted above used a 13-1/2 x 15 prop on your motor.

The best I could tell you is find a place that has loaner props or an exchange problem for this exact situation

 

[Scott Danforth]

I have no clue but I found a number of sources which list the range of a 4 stroke Yamaha as 180-210 PSI

goes to show how much BS is on the internet.

your cranking PSI is ball-park your compression ratio times 1 atmosphere. so a 9.5:1 compression ratio will be about 140 psi. it was true in 1862 and when Nicolaus Otto built the first 4-stroke in 1861, it is still true today.

from the Yamaha 250 manual. minimum, 89 psi (the motor has a compression release)

from the yamaha 115 manual minimum 135 psi (no compression release)

 

[dingbat]

your cranking PSI is ball-park your compression ratio times 1 atmosphere. so a 9.5:1 compression ratio will be about 140 psi.

Comments on this paper?

If you adjust for the specific heat to your 14.5 atmospheric pressure you end up with 20.3 x 9.5:1 give you a compression of 192 psi

http://www.healey6.com/Technical/Nominal%20compression%20pressure.pdf

 

[Scott Danforth]

Comments on this paper?

If you adjust for the specific heat to your 14.5 atmospheric pressure you end up with 20.3 x 9.5:1 give you a compression of 192 psi

look at the last table of the PDF you posted. 9.5:1 cr is about 150 psi on the gauge

 

[WinsLetshawn]

Пoing from a 19/4900 rpm to 13/6000 rpm will reduce your top speed even more. I think prop pitch is not going to solve a problem such as too fast a troll. Let`s assume he is now trolling at 3.3 mph and wants to slow to 2.2 mph, That is a 1/3 reduction in speed which means that a 17 pitch prop would have to change to a 12 or 13 pitch to accomplish it. Because simcasts prop pitch is a measurement of inches travelled for each revolution that directly relates to speed. Get a tack installed and feel free.

 

[Sea Rider]

If the tach is right and the motor ir revving at wot with a 19 pitch at just 4800 revs as loaded, it's revving 1500 revs under from its max range, if the +,- 200 RPM loss-gain per pitch rule of thumb would be applied will need to drop 7 pitches to a 12 prop which sounds insane....

Happy Boating​

 

[QBhoy]

The numbers here don’t really make sense. Despite that, natural instinct would suggest that a 19 shouldn’t be too far off what you need. Or within a couple inches anyway. No way it should have a 13” on it. You’d think. Are you trimming up ? Is the boat bow heavy with gear and bow ploughing through the water ? Is this the original engine ? Is it too low on the transom ? Do you have a silly hydrofoil fin on the engine or similar ?

 

[agarabedian]

Hey everyone just giving an update. I switch to a turning prop stainless steel 13.5x15 and what a world of difference. It feels like a completely new boat!!! Fast and nimble and pulls great. Still only at 5200 rpm now so might try a 13 pitch next!

 

[Texasmark]

Hey everyone I’m struggling. I have a 2006 Wellcraft fisherman 180 center console with an 06 Yamaha f115. It maxes rpm at 4800 and speed is 25. It currently has a 13x19 prop and I’m stuck on what prop to try. It’s a big investment and every “prop calculator” gives me a different answer. I am mainly looking for something that is good all around and won’t make my boat feel underpowered but will get me to the desired 6000 rpm range.
I just serviced the fuel injectors and cleaned all the fuel filters as I originally thought that was it lol. Any help is appreciated!!!

thank you

I would looked up your boat and as close as I could come was a 252, 25' Fisherman CC with a 150. Looking at the wetted surface such that the wake crosses the chine at the transom tells me the 150 is having no problem driving that hull. With that said I would imagine the 115 would have no problem driving your boat.

Go fast prop slip calculator says your engine with a 19P prop would drive your boat 54 mph with zero slip and 50 with a 7% slip at 6k RPM. If your hull is similar to the 252 I see no reason for anything less with a light load. Figuring dirty hull or wrong prop, bring slip up to say 12% would still get you 48.

Currently you are running 54% slip....something is dreadfully wrong....Your ear can give you an idea as to how your engine is running in a quick check, is the tach off....at 4800 it would be humming....at 6000 it would be singing.

At 25 mph, your wake closure behind your boat would be 6-8' behind the boat....at 45 it would be 20-25'. At 25 the wake would clear the chine of that boat about mid ship....at 45, clear at the corner of the transom.

So there are a few SWAGS to help you direct yourself to possible instrument failure. Otherwise dyno the engine.......