7.4L TBI fuel pressure problems

[390Express]

I've dealt with this a ton. FWIW, I don't think you'll have a fuel pressure problem. The TBI system runs fairly well from 11 psi - 14psi, and I've messed with mine to ramp it up to 19 psi, and didn't effect much.

Make sure you clean your flame arrestors, use the proper heat range spark plugs, have good wires, and if pressure, & octane are both good (run at least 91) look into replacing your injectors. I bought brand new BW injectors for around $90 each. (Brand new BW fuel pump for around $90 as well, I ditched the pierburg fuel pump, but it wasn't the issue) If replacing your injectors doesn't work, I would look next at your distributors. I think that is my problem. My port motor distributor varies in timing around 2-3 degrees at 3k rpm (bounces around slightly), my starboard motor (my problem motor) varies around 8-10 degrees. I'm replacing at least one distributor before spring. They're fairly inexpensive ($120ish per side, brand new).

[Cooler]

Hello all. In my comments about marinas changing to ethanol gas, I did not mean to imply that they were slipping by, or in any way, misrepresenting the gas they pump. That is illegal anywhere I have cruised. What I meant to say was, a number of marinas are transitioning, with proper disclosure, but not informing boaters in any pro-active manner. Some boaters assume that because the fuel was non-ethanol last season, it is the same. Sometimes those pumps are not located where you can easily see them for disclosure tags, and the college student pumping gas is not going to know what you expect. I have had a number of customers come in to buy fuel treatments that were surprised their marina changed, and they did not realize it until they filled the tank a couple of times. They simply changed fuel purchase locations, finding non-ethanol suppliers, so they didn't store ethanol treated gas for 7 - 8 months on the hard. It just feels like these performance problems, especially injectors clogging up, got more frequent as this transition started. er

[mjk1040]

Cooler, I didn't think that way, but feel there is a good possibility, and have been told via the delivery driver, that some sneaky marinas will buy 87 octane ethanol gas and have it put in the 90 octane non-ethanol labels! Many Consumer Affairs Departments are under staffed and do not test all dispensing units for the proper EPA standards as labeled.
On another note as to the TBI's, pull the air control valve and clean it or replace it. This may be the issue!

[Cooler]

Mike - those delivery drivers would be the only ones that really know. You must have to be really vigilant to keep good fuel in the tank. Once again I am thankful for the area I do my cruising. There are far less marinas in this area, and that keeps everybody pretty honest. The field inspectors are able to get to the marinas. The dock master at my marina is always whining because they show up at the most inconvenient times in terms of his schedule. He also knows that bad news travels fast, so if someone has a bad experience, and there have been a few, that station is the hot topic in the area. er
Note: we are getting a 12 - 14 inch snowstorm right now. Coming your way. Come on spring!

[390Express]

You can test your marina fuel for ethanol by taking a small vile, adding a small amount of water (maybe 1” from the bottom), marking the line, then filling it most of the way with fuel. Shake it up, if the clear portion at the bottom gets bigger, there’s ethanol in the gas, if it doesn’t, it’s good.

[Newer boater]

My mercruiser wrench said if I used non ethanol gas I would need his services a lot less. Lucky for me the marinas here all have rec fuel. On the dock it’s 3.95 a gal.

[390Express]

My mercruiser wrench said if I used non ethanol gas I would need his services a lot less. Lucky for me the marinas here all have rec fuel. On the dock it’s 3.95 a gal.

$3.95 is great. It was around $4.65 - $4.85 for most of last year up near St. Clair Shores.