Prop help. 194 funship

[Scott Danforth]

use your phone

 

[Jay1686]

That's what I tried to do.

 

[Jay1686]

Pretty sure it's one of the 280hp models

I was under the impression u go downgon pitch when swapping from 3 to 4 blades.

Either way my old 3 blade was a 14.5x19 n never saw above 40mph on it's best day.

 

[Jay1686]

Doing more digging and I'm finding that I may have been wrong about what my wot rpm should be for the engine.
found another chart saying it should top out at around 4200-4600rpm. Which currently puts me over by 400rpms roughly.

They say the limiter should be at either 5000 or 5500rpm. Which makes sense.

On occasion , say a sharp turn or circle while pulling tubers itll kick back and I'll have to quick shift to neutral n back to continue.. I'm assuming that's the rev limiter kicking me out of gear. Probably cavitation related as it only seems to occur around hard turns and big waves.

 

[Tycer]

It does perform better but not optimum with this prop.

I do like turning point for sure.

What do I need to find the right size?

Engine is in pretty good health. At least I feel I maintain it well.
Still it is my first boat. How do I make sure I'm getting true full throttle?

You need a different tachometer to compare with your dash tach. Buy or borrow one and check your dash tach at cruising speed and WOT. Go back and reread the above posts. Then accurately map your on- plane speed/rpm, speed at xxxx cruising rpm, WOT speed/rpm. Switch props and do it again. Post back here. These people are very knowledgeable and helpful but they need data.

 

[Jay1686]

I can do that with my current prop. But I need to get another prop to compare with I guess.

I found a 14.5x21. 4blade
Thoughts?
Or should I try n find a 19 pitch 4 blade

 

[Jay1686]

Correction, they make a 14x19, 14.5x19 and a 14x21 4blade.

Just need help figuring out which to try.

 

[Tycer]

I can do that with my current prop. But I need to get another prop to compare with I guess.

I found a 14.5x21. 4blade
Thoughts?
Or should I try n find a 19 pitch 4 blade

Sorry. I assumed you still had your old prop. One prop is enough.

 

[Jay1686]

Yeah old prop was toast lol

But I took it out this morning on glass, no wind.
Hooked up a buddies digital tach to check.

Both tachometers read about the same within 100rpms.

Wot 4900-5000 @ 38.7 mph
cruising at 30 mph at between 3400 and 3500 rpms

I imagine by plaining you meant once up on plane, the slowest I can back off without coming off plane?
That was 10-12mph at around 2600 rpms


Been reading bout diameter n pitch. Every inch of pitch added drops rpms about 200. And every inch I drop in diameter raises it about 500rpms. Is this correct?

Because if it is, I found a 14x21 4 blade turning point prop.

The inch drop should jump me to around 5500 wot but the pitch increase should put me around 4300 rpm wot.
a 19 should put me around 4700rpm

does this sound about right?

If so should I go with the 19 or 21?

 

[Jay1686]

All of this is assuming my current 5000rpms isnt just because of the rev limiter cutting me off at 5000.
just thought of that

 

[Jay1686]

Ok update:

Put on a 4blad 14x19 prop today.
Way to choppy out there to run an accurate test.

Planning wasnt too bad. And rpms topped out around a400rpms. Around 40mph.

But I was unable to trim out or get a good open run due to the chop.

I'll update again once i get out on a calm day n really get to work it out.

I have a 14x21 that should be in in a day or 2 so I'll be swapping out all 3 props and testing and recording the results.

I'll keep the 2 best performers and return the worst.

1 for a full boat load/water sports...
1 for normal family cruising...

Hopefully save a lil fuel?

 

[Scott Danforth]

you will never save enough fuel in a boat with a prop change to ever notice.

make sure you are propped so you dont lug the motor...... lugging the motor will kill the motor.

 

[Jay1686]

Lugging the motor??

Update:
Ok so I got a nice day n got out myself to try out a few props.
Water was glass

Prop stats:
1. 14x19 (favorite)
• 45mph 4700rp
• 30mph 3000rpm
• 12mph 2000rpm

2. 14x21
• 42mph 4600rpm
• 30mph 2800rpm
• 15mph 2600rpm

3. 15x15
• 37mph 4900 -5000rpm
• 20mph 3000rpm
• 10mph 2500rpm

So I'm gonna go with the 14x19 as my daily driver. I get good top end speed and cruise comfortably.

However this was just by myself. With 5 or 6 adults on board will be a different story. This prop should still work for the family I think.

But I may need a backup for full boat/towing/tubing.

Given the stats. Should i keep the 15x15 for that?

Or return the losers and pick up a 14.5x17?

 

[Jay1686]

Also noticed coming in today more smoke/exhaust than normal from my transom. Guage was pretty hot. No smoke in engine hatch.

Was figuring all the testing at different load at wot.

Thoughts?

 

[QBhoy]

Ditch the 15....but sounds like you have other more serious matters to concern yourself now. Smoking and high temps is not in any way normal, even prop testing...although perhaps my original fears around the 15” prop have came to reality ? Far too small a pitch. If the rpm was maxed out for any prolonged length of time...you may have some damage.

 

[Jay1686]

Oh great..
what should I look for in diagnosing the overheating?

Ditching the 15 altogether.
thoughts on a 14.5x17 for towing?

 

[Jay1686]

Thinking swap the impeller?