bertram31.com

Tropic Star Lodge has asked me to check with you guys and see if anyone is using (or knows anyone using) the Deere 4045 TFM engine....its 150 hp at 1500 RPM. They are trying to figure out what gear to put behind them in their fleet of B31s, which are pretty light boats vs. the ones most of us have. My gut is that something close to 1 to 1 would work.

Any info would be appreciated.

UV

What kinda speed do they want?

IS the 1500rpm max or cruise?

Bruce - I realized the same thing after I posted the gist of their email to me and posed the question back to them, waiting answer. I looked up the engine data sheet on boatdiesel.com and it's 150 hp at 2600 rpm.....peak torque is around 1500-1800 rpm so I'm not sure what they are looking for. The engine would need to be geared/propped to reach at least 2600 at WOT to keep from orverloading it, even if they are planning to cruise at 1500, which I doubt.

They set the governors on their 4-53 NAs at about 100 hp and they are normally 140 hp. The fuel burn on the Deere at 15-1800 rpm is incredibly low, which is a real big deal at TSL.

I'll clarify when I hear back from them.

UV

A 2600 rpm engine should use a 1.5:1 gear. Targeting a shaft rpm of 1600-1800. IMHO.

1:1 would not allow a large enough (dia)=(blade surface area) wheel to take advantage of the little diesels torque, 2:1 would require an odd ball pitch (very high), and slipage may be high, resulting in a loss of effiency.

For boats in this size, power and speed range, 1500-1900 "shaft" rpm seems to always work well.

I'm no prop guru, but I believe this generality applies here.

Scot - I agree....when I threw out the gut feeling about 1 to 1 I had not looked at the spec sheet on the engine, just the email from TSL that said the engine was 150 hp at 1500 RPM, which threw me off base. 1.5 woud be my choice too.

I've emailed back and forth to TSL a few times in the last day or so and they are in the "tire kicking" mode again on engines to replace their DD 4-53s as parts are getting real hard to come by. So far they have tried 170 Yanmars (use too much fuel), the dreaded Nannis (won't last past 1,200 hours)

UV

What cruise speed and burn are they trying to achieve?

18 kts is plenty for them and fuel as little as possible or as close to the 4-53s as they can get.

UV