Originally Posted by Nice Pair

I am running a 28 with 300 promax's, sporty lowers, bolted on the transom. I am a real world boater, I run with lots of fuel and 2 to 4 peeps and assorted boat gear.
I have always been made to believe that the 3 litres on a 28 makes it tail heavy. with that thought in mind, everything I have done is based off this belief. I am running oil bags to the outside, just behind the rear seat bulkhead.
I just moved the batteries forward of the front foot rest. I have dumped the heavy Skater seats for Sparko's. Prior to moving the oil bags approx 3' forward and moving the batts 8' forward I have seen (one time) 105mph with full tanks. (Bravo 32's with vent holes)

The problem: My props are showing more slip, my motors are seeing the rev limiters, and I've lost 5+ mph. The boat does not respond to up trim @ high speeds. Have I moved the center of gravity that far?

Sorry for all the wind, Thanx in advance, NP

Originally Posted by da*****rcury

Moving all of that forward, it sounds like you have lowered the angle of attack and now have more wetted surface and hence more drag=more prop slip.
How many batteries, how much do they weigh? I know that my optimas weigh over 50 lbs each. The fact that you lost 5mph and trim response with the move confirms your hunch about changing the balance.
I like running merc offshore cleavers on cats. I'd say go with the advice on the Dewalds or BBlades, and put the batteries and extra cables back where they were.
I've personally witnessed skater 28 w/300 promax and merc 3 blade 15x34 running over 110+

Originally Posted by supercat

I raced a 30 motion with 2.5's for years. To answer your original question, yes moving the batteries that far forward will absolutely make that much difference! 50lb eight feet is allot!!!!! The question is how does the boat launch and land? Yes you can get more speed with everything in the back but the attitude of the boat won't be flat. I ended up with a 25# bag of lead shot in the very tip of both sponsons. The boat was a bit slower in calmer water (1 to 2' chop or less) ...but... the boat ran faster over all conditions when the boat left the water as I could keep speed up with confidence of not kiting the boat. BALANCE IS EVERYTHING IN THESE AIR ENTRAPMENT HULLS! That being said, the way mine was balanced I ALWAYS ran with neutral or slightly negative trim letting the air lift the bow. In my opinion you do not want to have to run a tunnel with positive trim.

Originally Posted by Nice Pair

10-4, it's starting to look that way. Got any 15x34x3's
Thanx NP (p.s. could I just add motors?)

Originally Posted by Double Rigged

Call Dave Dewald he will let you try a set. Tell him Ron from S Fla said to give him a call. His props will outrun Mercury ones any day and don't break blades. He will warranty them too.

Originally Posted by supercat

I raced a 30 motion with 2.5's for years. To answer your original question, yes moving the batteries that far forward will absolutely make that much difference! 50lb eight feet is allot!!!!! The question is how does the boat launch and land? Yes you can get more speed with everything in the back but the attitude of the boat won't be flat. I ended up with a 25# bag of lead shot in the very tip of both sponsons. The boat was a bit slower in calmer water (1 to 2' chop or less) ...but... the boat ran faster over all conditions when the boat left the water as I could keep speed up with confidence of not kiting the boat. BALANCE IS EVERYTHING IN THESE AIR ENTRAPMENT HULLS! That being said, the way mine was balanced I ALWAYS ran with neutral or slightly negative trim letting the air lift the bow. In my opinion you do not want to have to run a tunnel with positive trim.