ok..prop experts...?

[jlh3rd]

ok
I'm attempting a chesapeake bay trip from the northern section to annapolis tomorrow.
I am running my 3 blade, 16x12 on my 115 hp CT motor right now. I can excede my max rpm with this prop when not pulling tubers or loaded down....just two of us...
I calculated fuel burn/ mpg last year for each 1000 rpm up to 6000..with just two on board......actuall, pretty linear...
I have a merc., 4 blade, 14x14 that I can put on and came with the motor...My max rpm was never more than 5800....but I never ran fuel/mpg calculations....

so generally speaking, would I get better mileage in the 3000 - 5000 rpm range with the 4, 14x14in comparison to the 16x12 ?
The boat is out front and it doesn't take 10 min. to switch...

 

[Bondo]

Ayuh,...... Generally speaking, boat motors are most efficient at 3200 to 3500 rpms,.....

 

[jimmbo]

You don't prop a Marine Engine for a particular Mid throttle Rpm.

 

[jlh3rd]

You don't prop a Marine Engine for a particular Mid throttle Rpm.

That's not what I asked
I'm NOT propping for anything........I asked a specific question out of curiosity....that's all.....
I've already "propped" the boat.....

 

[dubs283]

so generally speaking, would I get better mileage in the 3000 - 5000 rpm range with the 4, 14x14in comparison to the 16x12 ?

Probably not going to notice much if any change in fuel consumption unless you remove as much weight as you safely can

My go to is if fuel consumption is a concern, boating isn't for you

The only way to know for sure is to try it and compare. Keep in mind conditions out of your control can also affect performance

 

[jlh3rd]

Ayuh,...... Generally speaking, boat motors are most efficient at 3200 to 3500 rpms,.....

so, at 4000 rpm...I get 3.5 gph, 15 mph....
just wondering if the 4 -14x14 would improve any of the other two if boat is set to one........

 

[jlh3rd]

Probably not going to notice much if any change in fuel consumption unless you remove as much weight as you safely can

My go to is if fuel consumption is a concern, boating isn't for you

The only way to know for sure is to try it and compare. Keep in mind conditions out of your control can also affect performance

boating isn't for me?......sigh....
thanks, but jeez...it's just a curiosity....it's not a concern....
I wouldn't of spent $8000 on a new 115 hp merc replacing the 60 so I could pull teenagers on tubes if I was concerned about consumption....
......I'm not racing down the chesapeake...I'm cruising....

 

[dubs283]

....it's not a concern....

No concern no question, right?

Have fun, buy gas, go boating

 

[jlh3rd]

No concern no question, right?

Have fun, buy gas, go boating

eh..not the same..

 

[dubs283]

eh..not the same..

Hmm, not sure why you're posting synonyms. Perhaps you misconstrued my post

By "No concern no question" I mean if you do not have a concern (about fuel consumption) there's no need to ask a question

If you are really curious prop selection is strictly based on performance, e.g. you want to select a prop that meets the performance you desire while not causing any harm to the engine. Based on your posts it seems you have already done this

Anyone who practices with different props, either for fun or for a living will definitely have zero concern about fuel economy regardless of curiosity.

The only time fuel consumption is a concern is if it changes drastically in which case it most often has little/nothing to do with the prop

Enjoy your cruise

 

[QBhoy]

Hi. I can likely help here. I have a 2016 115 CT. What boat is yours on ?
I have 3 props I change between fairly regularly. I’ve tried a few others too.
I go between a 19” laser 2, 19” tempest plus and a 20” enertia. My engine is on a 19ft deep v narrow cuddy sports boat. Some accurately documented details below, if it helps.
19” laser 2
Top speed is about 43 mph generally, at around or just over 6000 rpm and occasionally on the limiter at that.
Cruising best speed is at about 3800-4000.
Over all…this prop is good top end, but not very efficient cruising, compared to the others tried.
Tempest plus 19”
Top speed is about 43/44 mph at about 6000 rpm give or take. Has hit the limiter once or twice if running light and hood off in a bit of chop.
Very very good efficiency cruising at anything between 3500-4000. Will do about 1.6/1.7 miles per litre of fuel at this and mid 20’s at least mph.
Very good at going slow in displacement mode too.
20” enertia
Top speed can occasionally see 45/46 mph at nearly 6000 rpm or a little less.
Without doubt, very quick in the right conditions. But will actually show less speed for the same rpm as the tempest does ! Less efficient for cruising and slow speeds than the tempest, but better than the laser.
I think generally I get about 4.5-5 mpg cruising.