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My Merc 425 has a best of 63, perfect conditions.  W

 

RPM

SPEED

GPH

MPG

2150

17

6.7

2.537

2600

26

8.7

2.989

2650

26.8

9.5

2.821

2700

27

9.8

2.755

2750

28

10.2

2.745

2800

29

9.9

2.929

2850

30

9.9

3.03

2900

30.5

10.4

2.933

2950

31

10.4

2.981

3000

32

10.8

2.963

3050

33

11.4

2.895

3100

33

11.7

2.821

3150

34

11.5

2.957

3200

35

12

2.917

3250

36

12.6

2.857

3300

36.5

13

2.808

3400

37.7

14

2.693

3500

39

15

2.6

3550

40

15.5

2.581

3600

43

18

2.389

3700

46

21

2.19

3800

49

24

2.042

3900

53

27

1.963

4000

56

30

1.867

4500

57.3

33

1.736

4950

58.7

35.5

1.654

5000

59.9

37

1.619

 

 

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I have the 375 hp Merc 496 Mag.  Best I've seen is 56-57 GPS in perfect conditions.  53-54 is more typical though.

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13 minutes ago, Buehlers Days Off said:

Thanks will have to wait and see this weekend.

Just enough ripples to break the hull loose, mid-grade gas, high barometric pressure, and temperatures under 70 degrees. Empty waste, water, and low fuel level, single passenger, canvas down, windscreen and transom door open, and trim up as much as the bow will tolerate. Oh, and leave any extra gear on the dock.    Only ever bounced mine off the rev-limiter one time and it was exactly that situation. Go for it.   W

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Buehlers Day Off!  Sorry, can't help you with your top end question but just curious, did you once marine in Racine, WI?   

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On 10/8/2019 at 8:22 AM, Wingnut said:

Just enough ripples to break the hull loose, mid-grade gas, high barometric pressure, and temperatures under 70 degrees. Empty waste, water, and low fuel level, single passenger, canvas down, windscreen and transom door open, and trim up as much as the bow will tolerate. Oh, and leave any extra gear on the dock.    Only ever bounced mine off the rev-limiter one time and it was exactly that situation. Go for it.   W

All that prep kind of reminds me of my prep back in the day when I would race someone with my 1968 15ft Mark Twain with a 110

hp. Merc.(that was the biggest motor they made back then, that they nick named  the tower of power) She would do 48 mph.

Back in 68 that was fast for the conventional boat, the only thing faster were the racing boats.

Then they came out with a 135hp. 

There was a guy that had one on a 18ft Glasspar that I raced,while I was sitting on the motor well, hanging onto the motor, at 48mph, we were neck and neck, that was back in my fearless days, how dumb was that.

Denny.

test076.jpg

 

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On 10/7/2019 at 8:42 AM, Wingnut said:

My Merc 425 has a best of 63, perfect conditions.  W

 

RPM

 

SPEED

 

GPH

 

MPG

 

2150

 

17

 

6.7

 

2.537

 

2600

 

26

 

8.7

 

2.989

 

2650

 

26.8

 

9.5

 

2.821

 

2700

 

27

 

9.8

 

2.755

 

2750

 

28

 

10.2

 

2.745

 

2800

 

29

 

9.9

 

2.929

 

2850

 

30

 

9.9

 

3.03

 

2900

 

30.5

 

10.4

 

2.933

 

2950

 

31

 

10.4

 

2.981

 

3000

 

32

 

10.8

 

2.963

 

3050

 

33

 

11.4

 

2.895

 

3100

 

33

 

11.7

 

2.821

 

3150

 

34

 

11.5

 

2.957

 

3200

 

35

 

12

 

2.917

 

3250

 

36

 

12.6

 

2.857

 

3300

 

36.5

 

13

 

2.808

 

3400

 

37.7

 

14

 

2.693

 

3500

 

39

 

15

 

2.6

 

3550

 

40

 

15.5

 

2.581

 

3600

 

43

 

18

 

2.389

 

3700

 

46

 

21

 

2.19

 

3800

 

49

 

24

 

2.042

 

3900

 

53

 

27

 

1.963

 

4000

 

56

 

30

 

1.867

 

4500

 

57.3

 

33

 

1.736

 

4950

 

58.7

 

35.5

 

1.654

 

5000

 

59.9

 

37

 

1.619

 

 

 

 

What pitch prop are you using?

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17 minutes ago, BajaDriver said:

What pitch prop are you using?

Rear 48-823666 24P 14.25

Front 48-823665 24P 15.5

Bravo III-X with optional 1.81 final drive ratio

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On 10/10/2019 at 7:05 AM, Denny said:

All that prep kind of reminds me of my prep back in the day when I would race someone with my 1968 15ft Mark Twain with a 110

hp. Merc.(that was the biggest motor they made back then, that they nick named  the tower of power) She would do 48 mph.

Back in 68 that was fast for the conventional boat, the only thing faster were the racing boats.

Then they came out with a 135hp. 

There was a guy that had one on a 18ft Glasspar that I raced,while I was sitting on the motor well, hanging onto the motor, at 48mph, we were neck and neck, that was back in my fearless days, how dumb was that.

Denny.

test076.jpg

Awesome story!

 

 

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