Recently purchased a 2007 Crestliner 1750 SC Fishhawk from local dealer. 2007 Merc. 115 EFI XL 4-stroke came w/ Merc. Black Max 13.25" x 17" prop. Hull wt. =1100 lbs., Motor wt. = 410 lbs. Total gear wt. = 400 lbs. W/ 2 people in boat (400 lbs.), boat planes very sluggishly. WOT @ 5800 RPM nets 37 mph(gps) but engine not fully trimmed. Trimming full out causes prop to ventilate. Cavitation plate appears to be approx. 1" lower than bottom of hull when motor is trimmed down to where the cav. plate is parrallel to hull bottom. Hard to tell where cav. plate is positioned on plane due to the intense spray between the cav. plate and the secondary lower unit fin. Motor is mounted such that the transom wrap-over bracket of the mount is 25" higher than the bottom of hull. Boat won't plane with 4 people (only additional 220 lbs, ya..they're light gals). Tried these other props w/ 2 people in boat:
Solace Amita 4 blade 17p - Better hole shot - 5400 rpm WOT 38 mph- @80% trim, prop ventilates. Solace Amita 4 blade 19p Hole shot similar to merc. prop - 5200 rpm WOT 39 mph, @80%+trim, prop ventilates. MW Ballistic SST 3 blade 21p - Hole shot sluggish-5800 rpm WOT 39 mph, able to fully trim without ventilation.
The only prop that I think would even come close to being able to plane boat w/ 4 people is the 17"p Amita 4 bladebut hole shot would be sluggish. Dealer ensures me this rig is set up the way I want it. I don't think so. It seems I should be able to prop it, or change motor height on transom to get mid to upper 40 mph out of this rig w/ one prop (2 people), and sacrifice some top end for a hole shot that would just about yank the arms of a skier off with another prop. WOT throttle range for this engine is listed as 5800rpm - 6400 rpm. Anybody got any ideas as to whether or not the engine is mounted @ the proper height, and what I should be looking for in a prop? My experiments are getting expensive.
Solace Amita 4 blade 17p - Better hole shot - 5400 rpm WOT 38 mph- @80% trim, prop ventilates. Solace Amita 4 blade 19p Hole shot similar to merc. prop - 5200 rpm WOT 39 mph, @80%+trim, prop ventilates. MW Ballistic SST 3 blade 21p - Hole shot sluggish-5800 rpm WOT 39 mph, able to fully trim without ventilation.
The only prop that I think would even come close to being able to plane boat w/ 4 people is the 17"p Amita 4 bladebut hole shot would be sluggish. Dealer ensures me this rig is set up the way I want it. I don't think so. It seems I should be able to prop it, or change motor height on transom to get mid to upper 40 mph out of this rig w/ one prop (2 people), and sacrifice some top end for a hole shot that would just about yank the arms of a skier off with another prop. WOT throttle range for this engine is listed as 5800rpm - 6400 rpm. Anybody got any ideas as to whether or not the engine is mounted @ the proper height, and what I should be looking for in a prop? My experiments are getting expensive.
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