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Old 05-08-2018, 01:03 PM   #21
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So the QSB 380 high idle is probably 3080 for a 3000rpm engine, the mechanical 6BTA 370 rated at 3000, high idle is probably 3200 or so.
On my original Cummins QSB 5.9L 380hp it only reached 2925rpm on sea trial. Ideally, it should have reached 3000-3050 meaning I am very slightly under propped. Not a problem considering how I run the boat. If I had a planing boat, I'd be happy with the 3050 rpm that the OPs engine hit at WOT during the sea trial.
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Old 05-09-2018, 12:12 AM   #22
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On my original Cummins QSB 5.9L 380hp it only reached 2925rpm on sea trial. Ideally, it should have reached 3000-3050 meaning I am very slightly under propped. Not a problem considering how I run the boat. If I had a planing boat, I'd be happy with the 3050 rpm that the OPs engine hit at WOT during the sea trial.
I think you mean you are slightly OVER propped? Since the engine doesn't reach full expected RPM?
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Old 05-09-2018, 11:20 AM   #23
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I think you mean you are slightly OVER propped? Since the engine doesn't reach full expected RPM?
I am pretty sure that is what he meant!
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Old 05-09-2018, 12:01 PM   #24
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I think you mean you are slightly OVER propped? Since the engine doesn't reach full expected RPM?
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I am pretty sure that is what he meant!
Yup, you are both correct. Over propped. Senior moment...
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Old 05-09-2018, 07:16 PM   #25
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The boat builder would match the engine transmission and prop so why mess with it?
If you want to try and make improvements, have the prop tuned to a higher standard.
If you start change the prop with the hopes the a governor will protect your engine and drive line from damage is just a tad bit foolish IMO.
The alternative is to contact the builder and ask what prop specs he would recommend to accomplish your goals.

My AT does not have a ''load meter". It does have a RPM readout.
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Old 05-10-2018, 03:27 AM   #26
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The boat builder would match the engine transmission and prop so why mess with it?
If you want to try and make improvements, have the prop tuned to a higher standard.
If you start change the prop with the hopes the a governor will protect your engine and drive line from damage is just a tad bit foolish IMO.
The alternative is to contact the builder and ask what prop specs he would recommend to accomplish your goals.

My AT does not have a ''load meter". It does have a RPM readout.
Not sure you understood the question. And the builder USUALLY props the boat to spec on an empty dry boat. Boats gain weight over time. Anyway, the purpose of this post is if there is any performance left on the table. He may even gain efficiency by adding pitch if he can. When I purchased my boat it was underpropped. I added some pitch and gained a knot or two and am right on the money with the prop. It ain't a science my friend....as much as you(or the manufacturer) might think it is. And nobody is trying to do anything with the hopes the governor is going to catch it.
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Old 05-10-2018, 04:02 AM   #27
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Not sure you understood the question. And the builder USUALLY props the boat to spec on an empty dry boat. Boats gain weight over time. Anyway, the purpose of this post is if there is any performance left on the table. He may even gain efficiency by adding pitch if he can. When I purchased my boat it was underpropped. I added some pitch and gained a knot or two and am right on the money with the prop. It ain't a science my friend....as much as you(or the manufacturer) might think it is. And nobody is trying to do anything with the hopes the governor is going to catch it.
Ah ha, now I do understand the question, I think.
Now, 'we" have to determine how much weight we added to the boat.
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