Rpms

[KEVMAR]

I️ have a 1983 36 albin 120 Lehman at what rpms do most run at .. I️ run at 1500 rpm and go 6 knots . Wondering if we should go up to 18? Thanks for the input

 

[psneeld]

I run at 1650 to 1700 rpms and get 6.3 knots. Any more and my wake starts going up dramatically as does fuel burn.

1800 to 1850 if I need a half knot to make a bridge.

 

[jleonard]

I usually run 1650 to 1750 and get roughly 6.5 knots in no current.
I have been known to run 1900 at times, but I prefer to keep the rpms down.
Not a fuel thing for me as there's not enough difference to even consider, just thinking longevity.

 

[Gbinterim]

I run at 1700 which gives me 7 knots using a 4 blade prop on a Ford Lehman 120. Higher rpm’s just increase the noise level.

 

[High Wire]

Should have room for another 100 to 200. Wont hurt to try it.
Make a simple rpm/speed table 100 rpm increments. When you get to where 100 rpm boost only raises speed 0.1 knot, no point in going further.

 

[PM]

I always ran at 1750, doing about 7 - 8 kn. I met another owner with a basically identical boat, He said he runs his W.O.T., up around 2,400, close to 10 knots. American Diesel seems to agree with him. He said it improves speed and barely changes mpg which is so high anyway that what difference does does it make if it's a little worse. I get about 1 to 1.5 gls per hour which translates to around 4 -5 mpg. My problem is not burning enough fuel to keep it fresh, maybe this year, now that I am retired...

 

[Ski in NC]

Second post #5. Start at 1200 and write down speed. Go up 50 or 100rpm and write down speed. Somewhere around 7-8kts an additional 50rpm will net almost zero speed increase. Your optimal rpm will be like 100rpm below.

16, 17, 1800 are all within the happy spot for that motor.

I would not recommend running it at full power continuously (post #6). It's a tough engine, but not that tough.

 

[swordfish]

33 ft boat
120 ford bowman

cruising speed
1350 rpm
5.5/6 knots (no current)

max speed
2000rpm
8 knots