Hey guys. I need a little prop help.
I have a new Crestliner VT 18 with a Mercury four stroke ProXS 115hp.
The motor is in the second hole from the top.
I ordered the boat with the a Spitfire X7, but it was on backorder so the dealer put a BlackMax 17p on it. With the BlackMax, I'm hitting 5500 rpm with no trim and hitting 39mph. I can trim it one or two blips to get to 5900rpm and 42 mph. Beyond that it starts to porpoise significantly. I have trimmed it up to 6300rpm and hit 49mph, but it was not pleasant; it was like riding a bucking bronco.
The dealer sent me the Spitfire X7 19p. With it I'm getting 4600rpm with no trim and 36.5mph. I can trim it up to 5000rpm and 42mph where it begins to porpoise. Beyond that there is significant porpoising.
I know most people are pairing the 115 ProXS with the 19p X7, but it doesn't seem like I'm getting nearly enough rpm or performance. Mercury has a performance sheet showing 6150rpm and 50.5 mph with the Crestliner TC18, which I think is the same hull. They also report mounting hole 2.
I don't carry a lot of weight in the boat but I did try shifting around what I do have and it didn't make a difference.
Any suggestions? I'll reach out to the dealer too, but I wanted to try to educate myself a bit before I do so.
Thanks all.