Rebel_Heart

I have a twin engine 35' boat which came from the factory with 502 mpi's. I was turning the 26 Hydro's at about 4800 wot - 75mph. Last season I had AZ Speed upgrade the engines with an MSD ignition, K&N filters, CMI headers (got rid of silent choice), more aggressive cam, ECU upgrade, Dart Pro One aluminum heads, Crane gold rocker arms. I increased rpm's to 5,300 wot - 80 mph (gps).

I am not happy with the top end, although the low end and mid range is fantastic. The next step after talking with Jim at AZ is to bore to a 540 with upgrades to the lower part of the engine. I have not had it dynoed, although I am told that it should have increased from 415 to 515 hp. This next step should increase a little over another 100 hp, with a considerable amount of torque.

Is the route to go? I have always stayed away from superchargers, but would like to see the boat near 90.

Will any of the setback boxes help my cause? Thanks.

deboatmon

I'm not an engine guru by any means but it seems that with an additional 500 RPM and the MPH you are running at, you probably should have been able to pick up closer to 7-10 MPH with those mods. You may be ready for some prop work. It seems to me like 500 RPM should have given you more top end. You've probably gone to 470-490 hp and it seems to me that should have added more top end. Just like you said.

I'm surprised that you had no dyno time. You spent some pretty heavy cash to do what you did and it's just possible your expectations came up short because of a lack of a real "dial in". I believe very strongly in dyno time for your level of modification.

Good luck and let us hear where you end up at on top end.