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Old 02-02-2017, 05:46 AM   #1
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How many Knots develop or what is the cruising knots for a Maxum 3500 SY with two Cummins 4BT 3.9 (250 hp) Diesel engine? All testing has been made with gasoline engines. I can't find that information!


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Old 02-02-2017, 02:44 PM   #2
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knots are somewhat irrelevant. Heading into wind, waves, current, or tide will much different than running with them. At the same RPM with a 3 knot tide, you could be running at 20 knots heading into the tide, or 26 knots running with it.

I shoot for an RPM window. If that translates to a speed that is too high for the sea state, then I slow down or attempt to modify my angle of attack to soften the ride. More often the speed is dictated by the sea state.

Determine what the max rpm of the engine is, then subtract between 10 - 25% for targetted RPM range. You're amx speed will be dictated by RPM and sea state.

Trying to use speed at the metric for measurement is a bit like the tail wagging the dog.
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Old 02-02-2017, 03:24 PM   #3
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Thank you! My question is because I bought a 2006 Maxum 3500 SY without engines and transmissions. I have been in search about engines. The vessel had Cummins 4BT 3.9 (250 hp). I found two Volvo Penta KAMD 44 PECD (260 hp), but some mechanical specialist said that engines hasn't enough hp for that boat. I found some information that show a 40 feet vessel with that engine and 4,000 pound heavier, developed 20-25 knots at 3500 rpm and 28-32 knots at 4000 rpm. I am very confuse about to buy the KAMD 44 Volvo Penta (260 hp) or a Caterpillar 3116 (350 hp), which is more expensive and need to buy the v Drive transmissions for them!


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Old 02-26-2017, 11:45 PM   #4
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A 2006 with no engines? I might be able to understand that if they were gasoline, but those Cummins engines are worth some money! Sounds like someone sold them off to try to wring some money out of the boat.

How much did you pay for this boat? Did you have it surveyed?

If you repower with different engines, you may have to change electronics and throttle controls and other things.

First I would find a local mechanic who has experience with diesel repowers.
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Old 02-27-2017, 12:58 PM   #5
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To my knowledge, these boats were offered with Cummins 6BTA engines.
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Old 02-27-2017, 01:00 PM   #6
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Thank you! This boat was bought with Cummins 4BT3.9. I have the sale bill specifications.


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Old 02-27-2017, 01:02 PM   #7
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I must be looking at an upgrade option or later models.
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Old 02-27-2017, 01:05 PM   #8
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I get an offer for two Caterpillar 3116 (350 HP), but i need to change or buy two ZF 85 transmission. Right now I have two Volvo Penta KAMD44 (260 HP), but need all pulley and vibration system.


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