Tank filling question
 

I didn't know I had an issue filling my tank until yesterday, or even if I have an issue... All last year, I simply put the fill nozzle in & filled until the fuel spit out the vent. The gauge would read full, & I accepted it as full.
I did know that I had a poorly operating float, it would move all over the place so I upgraded to a solid state float tube sytem, & so far it works very good...But now my issue.
Over Memorial weekend, I ran out...No problem, I put 5 gal in & put it on the trailer & pulled it home. Yesterday, I went to fill it up, & it would only take 70 gals before it spit out the vent, the problem is, this is a 100 gal tank, I even looked down the fill neck & saw fuel. When I got to the boat ramp, I checked the fill neck & saw no fuel.
I ran about 70 miles yesterday, & the gauge is now reading a tick above 1/4.
So, today, I pulled the sender out, & measured exactly how much fuel is in the tank. If I did my math correct, I have about 40 gals of fuel in the tank now. That doesn't add up, so I'm thinking I have an issue with getting a full 100 gals in the tank. I'm thinking I must have had an air pocket & it would not allow any more fuel. Could this be due to filling too fast? Or could this be a problem in the vent?
Sorry for the long explanation, just not sure if I have a problem, or do I just need to slow down the filling.

Sounds like your fill and vent hoses are at the back of the tank. When boat is not level bow to stern you get an air pocket in front of tank. If you level the boat on trailer you may be able to fill it all the way but when boat goes in water you will lose alot of it (fuel) from the vent.

I know that I cannot get my tanks competely full when filling on land, even though fuel will spit out the vent. I would guess yours is the same way. You may also have had air pocket.

To check all this, I would fill the boat on land and then put it in the water and run it for 5-10 miles. Then fill it the rest of the way on the water and see how much fuel it takes.

Thanks for the input.
The boat not being level was not something I had considered. It's not noticeabley "un-level", but perhaps it is just enough to create the air pocket.

Griff, I will try filling on the water to see what that does for me, it does make sense, now that I think about it.
BTW, the boat runs great after the complete refresh, I did not switch to the roller cam, I had a hard time justifying the cost....I really appreciate your input.

I don't blame you for not switching to the roller cam. It was a pretty pricey upgrade.

filling
 

have had this prob also on a few boats on the trailer it will fill drop it in and it will take some more fuel. boat sits level on the trailer and in the water on an angle. i would fill it on land see how many gallons. then drop it in and see if it will take anymore and how much more. Chris

I bought my 1985 Formula 242LS in June. Wasn't so confident in the trailer after a wheel bearing failed, so I never filled it past 1/2 tank (101g capacity). On vacation a couple weeks ago, I was heading to Martha's Vineyard to have a beer with the Prez, so I tried to fill the tank. It spewed out the vent/overflow at 3/4 full. I cruised about 15 miles, then tried to fill it again. This time it only took ONE gallon. I could see the fuel in the fill pipe. This weekend I pulled the rear seat and stuck my head in the engine compartment to look for a kink. I found the hose has been squished between the cockpit floor and the hull. Looks like it is restricted about 50%. Could this cause my "premature fillation"? Seems odd that I have no trouble filling the first 75g.

Thanks.

Look for a low spot in the vent hose. Fuel will accumulate there and prevent the tank from properly venting while it is being filled. Same with the fill hose. Want to guess how I found out????

Fill it up on the trailer.
Then jack the nose of the trailer up.
See if you can get more gas in it.

same thing just happened to me last week...ran out of gas in my port tank and then it wouldn't take more than 10 gal. fill a few 5 gal motorcycle tanks and get the tank at least 3/4 full...this will clear out the air pocket that formed.