Info on 1978 21' Hewes Marlin Construction

Yes, the side tanks go back behind the splashwell. They start 7 inches fwd of the transom. I also think that it will look better opened up.

 

How much total tankage do you have currently? We can assume the boat balanced well with them as they are, so moving them much farther forward wouldn't be wise. Centerline tanks, shaped to fit the V are common and this would be the route to go. You don't need a fuel cell, though a nice safety feature in cars, not as necessary on a boat.

Most of the specs on the boat can be determined with a tape measure and some math, so don't go crazy about it. A CG location might be handy, but again if the boat performed well previously, this might not be as important as you'd think, unless you make major changes to the location of heavy stuff.

 

Ok great. Not sure what exactly I want to do yet. I will figure it out after I have checked it out some more on the water with fuel in the side tanks and again with the fuel cell in position on the deck. I am sure testing in different configurations and in varying seas will be the most accurate.

 

The problem with fuel tanks well aft or forward is the trim alters according to how full the tanks are. Especially if they have large capacity and you travel long distances. That unusual tank set-up may explain why tabs are fitted. As you say, testing will tell you a lot.

 

What engine setup would be better if i upgraded the engine. A 150 with a 15 hp kicker or 2 75's?

 

About the Fuel tanks. What if i moved them FWD closer to CG and mount the base of the tanks below the sole so it is partially sitting deeper into the hull. I was told that these tanks are 35 gal. each tank. so i like that capacity. I would really like to ensure that this boat is well balanced. I will also have to ensure that the tanks are connected properly to ensure even consumption from each tank.