I have a MT 34 with a Ford Lehman 120hp and a Velvet drive. I feel like I have extra engine and could get a few more knots out of it. Currently at 1800RPM, I get 6knots. If I go to full throttle 2250rpm I only get 1 more knot. What propeller/pitch should I have on my Trawler?
Marine Trader 34: what propeller?
- Thread starter edrnemt
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
Welcome edrnemt!
timb
Guru
- Joined
- Sep 12, 2017
- Messages
- 572
- Location
- usa
- Vessel Name
- true heading
- Vessel Make
- marine trader 38 dc
that's not much less than what mine does (135). is that when you also start making a wake? so first post in 5 years . welcome to posting. sounds about normal to me . but I'm kind of new .
kapnd
Guru
- Joined
- Aug 31, 2013
- Messages
- 879
- Location
- usa
- Vessel Name
- #31
- Vessel Make
- ex-Navy MUB 50 fish/cruise
It’s a large, heavy boat with only 120 hp, so if you’re in a big hurry, you bought the wrong rig!
You might be able to optimize what you have with some careful data collection and the cooperation of a reputable prop shop.
Without LOTS more power, you must content yourself with a more leisurely pace.
You might be able to optimize what you have with some careful data collection and the cooperation of a reputable prop shop.
Without LOTS more power, you must content yourself with a more leisurely pace.
First your prop is over pitched. The engine should rev to 2,500 at wot not 2,250. A good prop shop can rework your prop to remove 2" of pitch which should get you close to 2,500 rpm at wot.
But that will make your speed less at 1,800 not more, but it will be lots better for your engine. Running it as it is pitched now is like lugging an engine in fourth gear up a hill whereas shifting down to 3rd will let it speed up and run better.
6 kts at 1,800 with an over pitched prop sounds like too low a speed. Is your bottom clean and/or the prop?
With your prop repitched you could run the Lehman at 2,000 rpm but it gets pretty noisy above that. 2,000 rpm should push a MT 34 with a clean bottom to 7+ kts.
David
