385 offshore fuel consumption

[Peggy-O]

I'm going to assume things didn't work out as you were hoping

[Kismet]

My apologies for the long delay in responding.

Here's where I am at with the prop change:

What was done: Center engine prop changed from 17" Pitch/3 Blade to 16"Pitch/4 Blade. New prop is manufactured by PowerTech Propeller

Performance:

1) Engine RPM on throttle up is more consistent across all three engines.
With the 17" center prop, the center engine RPM lagged on power up by as much as several hundred RPM until the boat planned out.

2) the boat planes out at 13.9kts and 3300 RPM. This is about 2KTS and 200 RPM sooner than with the old prop

3) The best performance on calm seas is 29MPH at 3650 RPM at a fraction over .9MPG. My goal was to get to 30MPH at under 3700 RPM which I could not get to no matter how I configured the trim planes or motor trim.

Fuel Consumption:
I put 200gals of fuel running the boat with the new prop. Each of the three fuel tanks is dedicated to an engine. Upon refueling, the center engine burned 10 gallons less than the other two. Before the prop change the center engine burned 20 gallons MORE than the other engines, so I am concluding that the prop change has improved the performance of just that engine but had a marginal improvement overall.

This begs the question: What if I replaced all three props with 4 Blade 16" Pitch props?
I am posing that question to the tech support guru at PowerTech

Downside:
The only downside is that the prop goes into gear with a louder bang than the 3 blade because of the extra bite and the hub is not the shift-dampening type that Yamaha props have.

The new prop cost $1200 including shipping. Three of them would be a heavy $4k investment all said and done.

If i can get to 30MPH@3700 RPM it would be worth it to me, since the Yamaha F350 Flywheel starts to accumulate time in the danger zone of 3750 - 4250 RPM range that requires a flywheel change after 100hrs of time in that range.
As a result, I rarely run above 3700RPM.

I will post again when I get a read from the good folks at PowerTech Propellers.

[Kismet]

My apologies for the long delay in responding.

Here's where I am at with the prop change:

What was done: Center engine prop changed from 17" Pitch/3 Blade to 16"Pitch/4 Blade. New prop is manufactured by PowerTech Propeller

Performance:

1) Engine RPM on throttle up is more consistent across all three engines.
With the 17" center prop, the center engine RPM lagged on power up by as much as several hundred RPM until the boat planned out.

2) the boat planes out at 13.9kts and 3300 RPM. This is about 2KTS and 200 RPM sooner than with the old prop

3) The best performance on calm seas is 29MPH at 3650 RPM at a fraction over .9MPG. My goal was to get to 30MPH at under 3700 RPM which I could not get to no matter how I configured the trim planes or motor trim.

Fuel Consumption:
I put 200gals of fuel running the boat with the new prop. Each of the three fuel tanks is dedicated to an engine. Upon refueling, the center engine burned 10 gallons less than the other two. Before the prop change the center engine burned 20 gallons MORE than the other engines, so I am concluding that the prop change has improved the performance of just that engine but had a marginal improvement overall.

This begs the question: What if I replaced all three props with 4 Blade 16" Pitch props?
I am posing that question to the tech support guru at PowerTech

Downside:
The only downside is that the prop goes into gear with a louder bang than the 3 blade because of the extra bite and the hub is not the shift-dampening type that Yamaha props have.

The new prop cost $1200 including shipping. Three of them would be a heavy $4k investment all said and done.

If i can get to 30MPH@3700 RPM it would be worth it to me, since the Yamaha F350 Flywheel starts to accumulate time in the danger zone of 3750 - 4250 RPM range that requires a flywheel change after 100hrs of time in that range.
As a result, I rarely run above 3700RPM.

I will post again when I get a read from the good folks at PowerTech Propellers.

[Kismet]

My apologies for the long delay in responding.

Here's where I am at with the prop change:

What was done: Center engine prop changed from 17" Pitch/3 Blade to 16"Pitch/4 Blade. New prop is manufactured by PowerTech Propeller

Performance:

1) Engine RPM on throttle up is more consistent across all three engines.
With the 17" center prop, the center engine RPM lagged on power up by as much as several hundred RPM until the boat planned out.

2) the boat planes out at 13.9kts and 3300 RPM. This is about 2KTS and 200 RPM sooner than with the old prop

3) The best performance on calm seas is 29MPH at 3650 RPM at a fraction over .9MPG. My goal was to get to 30MPH at under 3700 RPM which I could not get to no matter how I configured the trim planes or motor trim.

Fuel Consumption:
I put 200gals of fuel running the boat with the new prop. Each of the three fuel tanks is dedicated to an engine. Upon refueling, the center engine burned 10 gallons less than the other two. Before the prop change the center engine burned 20 gallons MORE than the other engines, so I am concluding that the prop change has improved the performance of just that engine but had a marginal improvement overall.

This begs the question: What if I replaced all three props with 4 Blade 16" Pitch props?
I am posing that question to the tech support guru at PowerTech

Downside:
The only downside is that the prop goes into gear with a louder bang than the 3 blade because of the extra bite and the hub is not the shift-dampening type that Yamaha props have.

The new prop cost $1200 including shipping. Three of them would be a heavy $4k investment all said and done.

If i can get to 30MPH@3700 RPM it would be worth it to me, since the Yamaha F350 Flywheel starts to accumulate time in the danger zone of 3750 - 4250 RPM range that requires a flywheel change after 100hrs of time in that range.
As a result, I rarely run above 3700RPM.

[Kismet]

My apologies for the long delay in responding.

Here's where I am at with the prop change:

What was done: Center engine prop changed from 17" Pitch/3 Blade to 16"Pitch/4 Blade. New prop is manufactured by PowerTech Propeller

Performance:

1) Engine RPM on throttle up is more consistent across all three engines.
With the 17" center prop, the center engine RPM lagged on power up by as much as several hundred RPM until the boat planned out.

2) the boat planes out at 13.9kts and 3300 RPM. This is about 2KTS and 200 RPM sooner than with the old prop

3) The best performance on calm seas is 29MPH at 3650 RPM at a fraction over .9MPG. My goal was to get to 30MPH at under 3700 RPM which I could not get to no matter how I configured the trim planes or motor trim.

Fuel Consumption:
I put 200gals of fuel running the boat with the new prop. Each of the three fuel tanks is dedicated to an engine. Upon refueling, the center engine burned 10 gallons less than the other two. Before the prop change the center engine burned 20 gallons MORE than the other engines, so I am concluding that the prop change has improved the performance of just that engine but had a marginal improvement overall.

This begs the question: What if I replaced all three props with 4 Blade 16" Pitch props?
I am posing that question to the tech support guru at PowerTech

Downside:
The only downside is that the prop goes into gear with a louder bang than the 3 blade because of the extra bite and the hub is not the shift-dampening type that Yamaha props have.

The new prop cost $1200 including shipping. Three of them would be a heavy $4k investment all said and done.

If i can get to 30MPH@3700 RPM it would be worth it to me, since the Yamaha F350 Flywheel starts to accumulate time in the danger zone of 3750 - 4250 RPM range that requires a flywheel change after 100hrs of time in that range.
As a result, I rarely run above 3700RPM.
[size=200][/size]

[Kismet]

Here's where I am at with the prop change:

What was done: Center engine prop changed from 17" Pitch/3 Blade to 16"Pitch/4 Blade. New prop is manufactured by PowerTech Propeller

Performance:

1) Engine RPM on throttle up is more consistent across all three engines.
With the 17" center prop, the center engine RPM lagged on power up by as much as several hundred RPM until the boat planned out.

2) the boat planes out at 13.9kts and 3300 RPM. This is about 2KTS and 200 RPM sooner than with the old prop

3) The best performance on calm seas is 29MPH at 3650 RPM at a fraction over .9MPG. My goal was to get to 30MPH at under 3700 RPM which I could not get to no matter how I configured the trim planes or motor trim.

Fuel Consumption:
I put 200gals of fuel running the boat with the new prop. Each of the three fuel tanks is dedicated to an engine. Upon refueling, the center engine burned 10 gallons less than the other two. Before the prop change the center engine burned 20 gallons MORE than the other engines, so I am concluding that the prop change has improved the performance of just that engine but had a marginal improvement overall.

This begs the question: What if I replaced all three props with 4 Blade 16" Pitch props?
I am posing that question to the tech support guru at PowerTech

Downside:
The only downside is that the prop goes into gear with a louder bang than the 3 blade because of the extra bite and the hub is not the shift-dampening type that Yamaha props have.

The new prop cost $1200 including shipping. Three of them would be a heavy $4k investment all said and done.

If i can get to 30MPH@3700 RPM it would be worth it to me, since the Yamaha F350 Flywheel starts to accumulate time in the danger zone of 3750 - 4250 RPM range that requires a flywheel change after 100hrs of time in that range.
As a result, I rarely run above 3700RPM.

[Kismet]

Short version:

Better on-plane speed
.1MPG improvement at cruise RPM (3700)
Better handling on turns in the slop
Better top speed at cruise RPM (29MPH @ 3700RPM)
Looking into changing out the outboard props with Merc ECO 17" as a trial to see it that has any benefit.
Won't be able to test until spring.....chat with you'all then....

[Kismet]

UPDATE:

I feel the 4 Blade 16" pitch blade is giving me better performance .....enough so to pursue making changes to the outboard engines as well (i.e., port and starboard).

Did a little more research and got some very good feedback on Merc Enertia ECO 17 Pitch.

I got a pair - one for the starboard engine (RH) and one for the port engine (LF). i will test them in the Spring and see if this gets me over .9MPG without sacrificing anything significant.

I got them from a dealer with a return policy so their is minimal financial risk as long as I don't crunch the props.

[kklige]

hi guys
running 385os looking to switch to 4 blades curious how you made out with fuel economy
thanks karl