It's your money. Obviously we can't convince you that it is not weight that is your issue.
Your assumption that the motors are doing their job is not accurate.
I'm no expert, but anytime I've been in a situation where troubleshooting is needed, rule of thumb is to start with the easiest and most likely, then work to the unlikely and obscure. There are zero signs it is weight. Scupper level, to noted performance differences on other boats between running light and fully loaded.
Pages have been written about fuel issues on boats, particularly with the advent of ethanol fuels, and the long off seasons for boats.
Hi guys - I had an interesting day on Friday and got to the bottom of this and it was the bottom(!). Many of you suggested this but I didn't suspect it because I never had a problem with bottom growth until now. I essentially discovered that Hydrocoat lasts a long time but not forever. I have been just touching up thin parts and the waterline and you can see there are no barnacles there but the whole rest of the hull was totally encrusted. I can't remember when I last repainted the whole hull and last year it was fine but not this year! Others at my yacht club are having problems as well so it must be a bad year for barnacles. A buddy with a big Hatteras said he couldn't even get it to plane so he hired a diver to clean it up.
So, convinced I had waterlogged foam because of my buddy's recent experience, I called a few marinas to see if they could weigh it with their travel lift. They said they could but suggested it would not be accurate enough. They said the the scale was graduated in 1000 lb increments and it could be off by a few thousand pounds. They were all really helpful. Boston Boatworks, said there was a truck scale nearby and suggested hauling the boat with their travel lift, dropping it onto their hydraulic trailer, and driving it to the truck scale. They called that a "long haul" vs a "short haul" and the cost was $21.5/ft ( $580.50). When they lifted it, we saw the bottom was totally encrusted with barnacles. That is visible in the video and photos.
They pressured washed it charging the higher rate ($6.25/ft) for a "heavily fouled bottom." Then they weighed it along with their trailer and large fork truck on the truck scale. The total weight was 40,040 pounds and they subtracted the weight of the hydraulic trailer and fork truck to arrive at a boat weight of 8020 lb which I think is about right for a 272 Sailfish. The dry weight without options is listed at 5500 lb, the motors are 500 lb each and ~50 gallons of fuel is 300 lb so I come up with 6800 lbs. I think I have all the options (hardtop, bow pulpit, microwave, fridge, freshwater system (which was empty), etc. so when that weight is combined with the weight of my tools and other gear, I think I am in the ballpark.
After they dropped me in I could feel the difference as soon as I put it in forward! I attempted a WOT test on the way back but conditions where not ideal. I did manage to get up to 5400 RPM and 38 MPG which is not the old numbers of 5800 RPM and 48 MPG but a whole lot better than 5000 RPM and 28 MPH. The fuel economy was ~1.2MPH which is not as good at the old numbers of 1.4+. I'm wondering if part of that is that bottom still has some residual part of the barnacles still present - the little round circles. You can see that in the photo of the bow. The guys were joking that the barnacle blue is better than superglue or any other manmade glue. I'll try to figure out how to clean that up further in the spring.
Thanks for all the help and suggestions - it is great to be able to tap in to the knowledge base in this community!
Cheers,
Duncan