Merc 2.5 carb runs out of gas at 6K

**CircleHook** · 02-26-2017, 05:25 PM

Little help Gents- Merc 2.5lt 200 hp 2002 carb - If taken to 6k and held there for over 30 seconds it runs out of fuel- 5k it is fine - tested with aux tank - did not run out of fuel-No question it is drinking faster than pump can pull from tank at 6k- Tank is 3 years old, gas line replaced last fall with best injector rated fuel line I could find ($5 a foot) new anti-siphon valve which is located right at tank. Boat is a 23' Mako- there is about 15' of gas line between tank and engine. Vent checked by loosing fill cap until about to fall off- no difference- Is this 15' simply too much to ask the stock diaphragm pump? Pump rebuilt last summer- What options? add electric pump? Is there a high performance pulse pump?

**eli** · 02-26-2017, 05:46 PM

15 foot to far will need electric pump

**CircleHook** · 02-26-2017, 06:48 PM

Originally Posted by eli

15 foot to far will need electric pump

That is what I expected- I really very seldom turn 6k but knowing it is close bugs me- I have an AIRTEX marine pump #33COFR183 - I used several years back on an Johnrude- Do I need to get fancy or just basic extra pusher? Regulator? bypass/remove pulse pump? and big question is how to wire? I had the Airtex on an auxiliary 12 volt feed from dash but was never real happy with this- can it be tied to ignition ? any way to set it up to shut off when engine dies? While I am not much of an electrician- I have a good friend who is excellent- I have a good spot to mount right above tank under center console.
This is pump I have-
http://www.ebay.com/itm/Airtex-E8337...-/310644103098

I got no problem spending a few bucks as needed to make this right. Thanks Gents

**johnboy 88 vegas** · 02-26-2017, 08:39 PM

The rev limiter is at 6k if you still have the stock cdm ignition system....just a thought unless your 100% sure it is fuel.

**eli** · 02-26-2017, 08:41 PM

Should be ok carb seat is fine at 6 psi try it may need a regulator, get a psi gauge so you can check psi at carb

**phillnjack** · 02-26-2017, 09:25 PM

put the pump under the engine cowl, otherwise you have a pressurised fuel line inside the boat and that is dangerous if anything should go wrong.
electric power can simply be put on the ignition, so when you turn the key on the pump starts up, when you switch
the engine off at the key so the pump shuts down.
can also put an aux turn off/on at the pump too. ( can act as emergency of switch)

just a thought

**transomstand** · 02-26-2017, 09:31 PM

Remove anti siphon valve, throw it as far as you can (be careful not to hit anyone), reconnect fuel line.

**CircleHook** · 02-27-2017, 07:23 AM

Originally Posted by johnboy 88 vegas

The rev limiter is at 6k if you still have the stock cdm ignition system....just a thought unless your 100% sure it is fuel.

Will rev limiter shut engine all the way down? I thought it just killed spark to a cylinder or 2?

**CircleHook** · 02-27-2017, 07:27 AM

Originally Posted by transomstand

Remove anti siphon valve, throw it as far as you can (be careful not to hit anyone), reconnect fuel line.

No doubt the anti-siphon valve is a fuel restrictor- I replaced it last fall because I was having to use primer bulb every time I stopped for a while.

**transomstand** · 02-27-2017, 08:22 AM

Originally Posted by CircleHook

No doubt the anti-siphon valve is a fuel restrictor- I replaced it last fall because I was having to use primer bulb every time I stopped for a while.

It's like having vice grips on the fuel line. Chuck it and you should be fine.

**W2F a V-King** · 02-27-2017, 08:46 AM

All of the above is good for sure, but is there a pick up screen on the fuel pickup tube in the tank in question?

I had a 23' CC offshore fish boat years ago with twin 2.4 200's and they pulled past 6K with stock pumps, through 3/8" ID fuel lines AND all connectors 3/8" ID. Sometimes a "3/8 inch" connector is not 3/8" ID...

23' Mako is a fine rig for sure !!

My son in Miami is looking for a boat like yours as we speak...

Just looked up that electric fuel pump, and it may not be as critical on line fitting size, because the fuel is electrically pumped....but it has 5/16" fittings.

Maybe OK, but just my .01

**Krazymaan** · 02-27-2017, 11:11 AM

I agree that running fuel uphill for 15' might be too much on they system.

**CircleHook** · 02-27-2017, 11:19 AM

I will test with anti-siphon removed- I only have a few weeks to get ready to take to FLA for the summer so going to work electric pump simultaneously-
Electric pump location- it has been suggested here to mount under cowl- I found an earlier thread that said mount close to tank down low-
Will an electric fuel pump provide an anti-siphon type function? What about pulse pump? go thur it or bypass it? Bypass I would expect.

**Krazymaan** · 02-27-2017, 11:29 AM

Bypass it for sure.

**Glasstream15** · 02-27-2017, 04:16 PM

Why do you want an anti-siphon???? Transomstand was wrong. When you throw that thing try to hit the SOB that invented it. I agree with the issue of pressurised (sp) fuel lines in the boat and in the bilge area. But you need the pump as close to the tank as possible. DOUBLE CLAMP all lines and inspect them regularly. Use all stainless clamps and replace every 2 years. And since you'll have plenty of fuel pressure, put a fuel/water separator filter close to the motor.