Installing fuel-water separator bracket and filter and I had questions

[eavega]

Hi

So I am wanting to install a fuel water separator on my 1988 Mercruiser 3.0 L. Silly me thought these things were standard, and I just ordered the bracket and filter kit, as well as the fuel hose barbs connections. I got everything 1/4", which I now know is wrong. So, my problem is that I can't really tell what hose size I should be using. The fuel line from the tank to the fuel pump has a bunch of markings on it designating that it is marine fuel hose, with some compliance numbers, and right at the end the hose is marked 0.5" I think, its not terribly clear. Anyway, I measured the inside diameter of the line, and it is a bit less than 1/2", which leads me to believe it is actually 3/8" id. Dos this sound right? The manual doesn't specify the fuel line diameter size, it just says that it should be a minimum of 3/8", but larger if its a long run. I can't find a 1/2" port fuel water separator bracket, nor can I find a fitting that has the 1/2" barb with 3/8" threaded fitting. Will I be all right using 3/8" fittings/bracket? I'd rather replace the four feet of fuel line from the tank to the fuel pump than have to hunt around for what are apparently hard to find fittings.

Opinions?

Thanks for any information you can provide.

Rgds

 

[Eric 3.7LX Alpha 1]

Re: Installing fuel-water separator bracket and filter and I had questions

You will be fine with the 3/8" line and fittings.

As long as there are no restrictions or kinks in the line it will flow plenty for your engine.

 

[Levithan]

Re: Installing fuel-water separator bracket and filter and I had questions

definetley 3/8.

 

[eavega]

Re: Installing fuel-water separator bracket and filter and I had questions

Okay, so I re-ordered the bracket with the 3/8" fittings, and installed it last night. I am waiting for one more part (thermostat) to put everything on the motor back together again and do a driveway test.

I had a question about the modified fuel system; So having cut my fuel line and installed into an empty can filter, I can only assume that the fuel pump should be able to draw fuel from the tank through the water separator filter, and down the rest of the line. While that is all happening, I would assume that the motor will not run, since there will be no fuel going into the carburetor.

Does anyone know whether I should just crank the motor until it starts and let the fuel pump do its thing until all the air is purged out of the fuel lines, or should I "prime" the fuel line to the pump to avoid having to pump air through the fuel pump until the line/filter is full. Will pumping air possibly hurt the fuel pump diaphragm?

Dose someone know how long it should take the fuel pump to draw the fuel through the fuel line and fuel/water separator? I ask that so I can determine when to stop cranking and start looking for another cause should the motor not start up.

Thanks in advance for replies.

 

[Bondo]

Re: Installing fuel-water separator bracket and filter and I had questions

Does anyone know whether I should just crank the motor until it starts and let the fuel pump do its thing until all the air is purged out of the fuel lines, or should I "prime" the fuel line to the pump to avoid having to pump air through the fuel pump until the line/filter is full. Will pumping air possibly hurt the fuel pump diaphragm?

Ayuh,... It don't hurt to pre-fill the canister filter, it'll save some of the starter's life...

No harm, no foul on the fuel pump....

 

[Don S]

Re: Installing fuel-water separator bracket and filter and I had questions

If you already have it installed, just poor a little gas into the carb and start the engine. You may have to do this a couple of times to get it primed but it will prime very quickly if you don't have air leaks.
Normally, if the carb is full of gas, and the engine is warm it will prime on just the fuel in the carb. Little tougher on a cold engine.

In the future, just pre-fill the filter with clean gas before installing.

 

[eavega]

Re: Installing fuel-water separator bracket and filter and I had questions

Just wanted to post a follow-up. Since I had already installed the canister, I didn't want to pull the can off to fill with gas and re-install, so what I did was pull the line from the fuel-water separator to the fuel pump, and used my siphon pump to pull gas from the tank through the separator. I heard the can filling, so I figure it was all good.

I guess there was still some air in the line, because the boat was hard to start, and once I got it started, I had problems rolling on throttle for a little bit. Whatever it was, it worked itself out within 10 minutes of starting the motor, because rolling throttle and/or starting the motor gave me no further problems for the rest of the day.

For the record, it was a perfect day on the lake. I think I saw 3 other boats on the water, no wind, water was flat as a dinner plate.

Bring on the summer!

Rgds