Fuel starvation from built in tank

Hey guys I just started with Iboats forum and I have a question. I have a 79 Johnson 100hp on a 88 bayliner 17' with builtin tank. I had problems last year as well. I made a winter project out of the boat. completly flushed the tank. Now with new floor and everything new I still get a loss at full throttle after a few minutes. I have in this order Tank, inline glass filter, fuel/water seperator, bulb to motor. Idle is good and very low speed is good. I checked the fuel pump and found damage. Installed a new one today. Took the boat out and still have the same issue. I took an a portable with me and after the problem I hooked it up and the motor ran fine at full throttle. I am using an attwood fuel/water seperator and johnson oem bulb and hose 5/16. The tank only has a barb fitting not a antisyphon valve. The vent line is completly clear. The service manual says to keep the tank to the fuel pump under 24" and mine is about 21". What am I missing? I would appreciate any help. I don't want to just use my built in tank for a fuel storage. Thanks.

Re: Fuel starvation from built in tank

What size hose did the portable tank have? I think a V4 engine needs a 3/8 hose. Check all the connections and make sure you are not sucking air somewhere. Since it runs properly on portable tank, at least you know where to look to repair your problem.
What is the flow rate on your seperator and what micron filter is in it?
Is the inline filter rated for 2 cycle engines and what micron rating is it?
You could bypass them one at a time and see if the engine runs properly.

Re: Fuel starvation from built in tank

I'm with the Commander. Sounds like you are sucking up more fuel from the tank than air can be replaced. Are you sure the vent is not partially blocked?

Re: Fuel starvation from built in tank

Thanks guys. I noticed that the Johnson bulb kit I purchased has 5/16" hose. The Attwood seperator has 3/8 inlet and outlet but reduced to 5/16 barb. I put hose clamps on all barbs they appear to be tight. I will purchase some 3/8" hose and replumb the entire circuit to 3/8. I looked all over the package and the seperator and could not find a micron rating. I think i'll just purchase a Johnson OEM seperator. I thought aftermarket products maybe okay. Again thanks for the advice and I'll let you know the outcome. Happy fishing guys

Re: Fuel starvation from built in tank

5/16 hose is factory spec. for the 100HP. Check your anti-siphon valve; if your fuel system is all higher than the tank, you can safely remove it.

One full sized water separating fuel filter is more than adequate. Redundant fuel filters overload the fuel pump and are never necessary.

As to the Attwood filters, you might do a search on all forums to see what others have experienced. My experience is that you get what you pay for. http://forums.iboats.com/search.php?do=process

Re: Fuel starvation from built in tank

Thanks I was hoping that the OEM bulb kit was sufficient. Do you think the Attwood seperator may be an issue? Also the glass inline filter before the seperator could be too much? I only put it in due to before I flushed the aluminum tank there was a lot of red sandy lookin substance in the tank. I wanted to see what was going to the seperator. Before I bought the boat someone replaced the antisyphone valve with just a barb fitting. I will get a new antisyphone valve and install it. Please excuse the miss-spelled words. As you can tell I am new to boats but I am learning quickly with the help and advice from guys like you on this forum. Thanks to you all for your support. I hope in the future I can offer the same to someone else.