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XDP-B Drive 2.32 swap ratio to 1.96

K

Kirdud

Member
Good day, Captains!

Due to unforeseen circumstances, one of my drives has failed. Fortunately, I’m lucky enough to have two drives XDP-B on my boat. I’ve come across some used drives as replacements. My current drives have a 2.32 gear ratio, while the new ones have a 1.96 ratio.

My current prop is an H7, but the props that come with the new drives are smaller. I’m considering two options:

  1. Replace just the failed drive and use either my current H7 prop or a smaller one to match.
  2. Replace both drives with the used ones and use the smaller props that came with them.
Could you please advise which option is better? How will these changes affect my boat’s performance?

For reference, my engines are 4.3L Volvo Penta, and the used drives are from a boat with 5.0L engines.
 
V6 engines and V8 engines have different HP and torque vs RPM curves and therefore, drive manufacturers design drive units with different
reduction ratios to get the optimum performance from V6 and V8 drives. When I bought my used 23 ft Lancer, could not get a propeller that
allowed me to get good performance... I pulled the boat from the water and marked the prop blade and the flywheel on the engine. I disconnected the ignition . I had a helper watch the propeller and count the revolutions, while I cranked the engine (counting the revolutions of the marked flywheel) for 10 revolutions.. Some simple math allowed me to determine the reduction ratio. It turned out to me the ration for a 6 cylinder engine. I swapped the drive for a V8 one ( see signature block below) and I was able to find a prop that "worked".... By definition, the "correct" prop on ANY boat is that prop, (pitch and diameter) that allows the engine to rev up to within the manufacturer's specified Maximum RPM range when the engine is full throttle in calm seas, normal number of passengers on board, a full tank of gas, and normal load of gear/equipment on board in correct tune.
For example MAX WOT RPM specified for my engine is 4200 to 4600 RPM.
 
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