Where is the best place/method to shut of the fuel when you tearinto the intake manifold/heads/cam etc of a 496HO 2005.

I have very full tanks.

They should not leak at all but the best thing to do is to pull the fuel hose from the tank to the motor and plug it with a bolt or something. The pickups in the tank are at the top with an anti siphon valve so it shouldn't be a problem at all.

hillbilly24,

Thanks for the information.

Do all fuel tanks have to have an antisiphon valve by law or something? I assume you mean the fuel tank outlet is at the top of the fuel tank when you say 'pickups in the tank'?

Thanks again!

USCG requires them to be installed but some builders don't, they can hurt performance slightly or stick and cuase a motor to run way too lean. If you own a Rage then your boat has them from the factory. Either way becuase of the desing of the pickup as long as you atrap the fuel line up to something higher then the top of the tank then it won't leak.

hillbilly24,

Thanks. Goog to know.

Hi HillBilly24

Don't mean to highjack this thread but I have a question on those anti-siphon valves in my Rage also. I've installed an electric fuel pump and accurate pressure guage when I added the Whipple Kit to my 496. On my starboad tank the pressure is a solid as a rock. On the port side tank the pressure runs up to about 45 and then drops down to 40 and then back up and then down again. I checked that all the fittings were tight but still have that proplem on that tank only. My pump is lower that the top of the tank so I'm not sure about discarding the valve - can they be cleaned or new ones purchased? Thanks!

Yeah you can buy new ones for about 5 bucks at any marine parts house like West Marine or your local shop should carry them. Boat builders like to use teflon tape for some reason when they plumb fuel systems even though they have been told a bilion times by the OEM engine manufacturers not to. It flakes off and plug alot of things including anti siphon valves. I would not recomend discarding the anti siphon valves. They are suppost to require 1 inch or less of vacumn to open and the total vacumn on your fuel sytem should be less then 2 inches. You can just tee a vacumn guage into the fuel line after the tank selector valve and then run it on both tanks and this will confirm that the problem is some where in the boats fuel system not the engine's. The anti siphon valve itself just looks like ahose barb that is scewed into the fittin in the top of the tank, when you take it off you will see that there is a check ball and a spring in it. Some of them can be taken apart and cleaned but for 5 bucks it aint really worth it and ussually if something has gone through them or is stuck in them it damages the seat that the ball sits on anyway which is part of the body and not replacable. Let me know if you have any other questions.

ComfortablyNumb,

Please tell me about your electric fuel pump. What is the maximum fuel pressure it can produce? Is the fuel pressure adjustable? Are special pressure gages required for fuel or will any work? What is the make and model and where did you get it?

Thanks!

HillBilly24, Thanks for your reply, thats great advice to verify that the problem exists in the fuel line before the engine. The boat is put up for the winter but that's something I'll check first thing in the spring before I start pulling things apart.

Rage, the whipple kit comes with an SX Performance electric fuel pump and the fuel pressure is adjusted with an SX Performance fuel pressure regulator. The installaion totally by- passes the factory fuel system after the stock fuel filter. I don't know how high you can go on the pressure but I'm reasonably certain that it can exceed what your stock fuel injectors would reasonably need. The stock setup on the 496 has 2 smaller electric fuel pumps and if I recall 2 fuel pressure regulators. I think that this has been discussed on these forums before. If you get the merc manual on the 496 the fuel section has a reasonable diagram on the stock setup.

I'm using an Autometer pro-comp marine mechanical fuel pressure guage to watch my fuel pressure. The whipple has a couple of ports for tapping in a fuel pressure guage but I don't know where you can tap in a separate guage on the stock system. But I'm sure you can.