Fuel line size?

[Smokinal]

I just picked up my boat from the shop, having some maint done and noticed they replaced the fuel bulb and line from the bulb to the engine. My question is, I just installed a water sep/filter between the tank and the bulb and the line size is 3/8. They used 5/16 from the bulb to the engine. Is this common or should the whole thing be 3/8?

1996 16' Nitro,,,75hp Merc

 

The bulb would have to have different size fittings on it to work properly too, no?

[Kevin22]

Should be at least 5/16. Merc uses 5/16 for almost all motors. 

[Smokinal]

3/8 is 6/16. My question is, is it common to step down the fuel line size after the bulb?

Why I ask is the bulb does not pump up hard like my old one did so I'm wondering, if the bulb has 5/16 fittings on it, the connection would be loose on the inlet side of the bulb possibly pulling air? It doesn't idle good, pops and dies.

I have an email into them but just curious of your thoughts as well.

[Kevin22]

Depends on the bulb. If they used an OEM merc bulb it is for 5/16 AND 3/8. The clamps keep the 3/8 snug as long as they used good clamps. They might have put a cheap bulb on, which could be causing your issues. Make sure they didn't use a tempo bulb, those are pure junk. Make sure everything has metal hose clamps, nothing should have zip ties or plastic clamps. These are the best style IMO http://www.amazon.com/AAS-Fuel-Injection-Clamps-FI8/dp/B0040CU0JA/ref=pd_sbs_263_3?ie=UTF8&dpID=31fDH7TFBsL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=01S701DM80JMBKCVJ3C9

 

[fishnkamp]

I just replaced my fuel lines on my 2010 Lowe Stinger.  The factory ran 3/8 line from the fitting in the tank to a thru deck fitting on the rear deck.  From here the system has a Mercury factory primer bulb and two pieces of 5/16 fuel hose.  The connection on the motor requires a 5/16 hose.  So if your 3/8 hose is tight on your primer bulb it may be fine.  I had to remove the hose from the motor and hand prime a lot to fill up the almost 10 feet of hose total until I had all of the air out.  Then I hooked it back up and pumped till the carbs were full and I had a rock solid primer bulb. You may have been air bound a little. Next time after you launch the boat prime it and let it run t a fast idle for a little time then go run it and see what it does. Good luck.

[Kevin22]

1 hour ago, fishnkamp said:

I just replaced my fuel lines on my 2010 Lowe Stinger.  The factory ran 3/8 line from the fitting in the tank to a thru deck fitting on the rear deck.  From here the system has a Mercury factory primer bulb and two pieces of 5/16 fuel hose.  The connection on the motor requires a 5/16 hose.  So if your 3/8 hose is tight on your primer bulb it may be fine.  I had to remove the hose from the motor and hand prime a lot to fill up the almost 10 feet of hose total until I had all of the air out.  Then I hooked it back up and pumped till the carbs were full and I had a rock solid primer bulb. You may have been air bound a little. Next time after you launch the boat prime it and let it run t a fast idle for a little time then go run it and see what it does. Good luck.

Merc engines are to be rain in neutral at under 2000 rpm at all times and not for extended amount of time per merc specs. 

If you haven't gotten it figured out yet I would absolutely take it back to the mechanic and tell him something is wrong. They should be able to hook it up to muffs on the spot and test it. I would say faulty bulb, probably has a bad check valve in it. 

Anyways, I have that motor series in 115 and while mine is rigged with 3/8 lines (double checked today while performing maintenance) it is spec'd to run 5/16 fuel lines. I would imagine yours is the same. So the fuel line and connections shouldn't be the problem unless they aren't properly clamped. I would guess he used 5/16 because that's what he had on hand and is all that is really needed. 

[Smokinal]

Well I did end up bringing it back to them. They rechecked everything and ended up replacing the needles in the carbs. They were the rubber tipped ones and they said they were worn out, causing excess fuel to go into the cylinders. I haven't tried it yet but they assured me it was running flawlessly.

As far as the bulb not priming hard, they said this new style Merc bulb is designed not to do that anymore. Something about Government fuel regulations (like how they made us change gas can fillers etc...) they said any new fuel bulb now has some sort of new style check valve that will properly supply fuel but not stay rock hard like the old ones.

We'll find out next Sunday. Thank you for the ideas guys.