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Michael, Master Mechanic
Category: Boat
Satisfied Customers: 257
Experience:  Over 25 years experience working on everything from PWC's to Mega Yachts
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I have a mercury 2007 225hp optimax. It's on a 25ft c_hawk.

Customer Question

Hi. I have a mercury 2007 225hp optimax. It's on a 25ft c_hawk . When I first got the boat I used a 18 gallon tank above the floor but now have switched over to the tank in the floor after pumping it out and looking in it with a bore scope to find that it was clean. It has a total of 4 fittings coming out the top. 1 is for the filler neck #2 is for the tank over flow # ***** runs to the motor and #4 Is I'm guessing a vent cause basically it's a hose that doesn't hook to anything. I have a racor filter set up with the screw on filter and a clear plastic cup that screws on the bottom of the filler with a drain. It that plastic cup supposed to stay full all the time and I'm supposed to drain it time to time in case of water. The problem I'm having is every once in a while the engine will start to lose power and surge while it's having these symptoms I can pump the ball up that is about 1 ft from the tank because it feels soft and when pumping it it does pump up and the engine clears up and goes on until it desides to act up again. The engine has a little vacuum difram pump that supplies the vst box and it has to pull fuel about 20ft and from the bottom of the boat. The supply line also has a total of 3 squeeze balls which I think is a little over kill and wander if that could make it harder for her to pull the fuel to the motor causing the ball to go soft and that little vacuum pump just don't have enough draw to pull fuelled 20ft and through 3 squeeze balls. So my question is would it hurt anything and do you think it would help to install a low pressure 3 to 9 psi inline electric fuel pump to help supply fuel to the engine and should I take some of these squeeze balls out ?
Submitted: 2 years ago.
Category: Boat
Expert:  Michael replied 2 years ago.

Hi my name is Mike,

There are a few things that could be causing this.....

First, to answer you question regarding the primer bulbs..... yes, each primer bulb does cause restriction in the fuel delivery and there should only be one so start by removing the other two and consider running a new fuel line so that you don't have splices in it. The only primer bulb should be near the motor and before the Racor filter.

As for the connections on top of the tank... The overflow and the vent are the same fitting and should lead to an thru-hull vent fitting. If there is a hose that doesn't connect to anything then that needs to be hooked to the vent or capped off.

Another issue here could be the screen on the pick up tube (if it has one) is plugged or the anti-siphon check valve at the fitting on top of the tank has failed. (should allow fuel to pass thru toward engine but not back into tank).

The vacuum operated diaphragm pump on the motor is also a culprit here and have a wear life and are known to cause fuel starvation issuers. They are rebuild-able but I recommend replacing the whole pump.. here is a link to a parts diagram and listing for the pump.

The racor filter is also a water separator and you are right about periodically draining the bowl to check for water...and yes, the clear bowl should always be full.

If the fuel system is set up and working correctly there should be no need for an electric booster pump so try these suggestions first and this should take care of your issue. Let me know if you have any further questions and I will continue to assist you.

I hope this helps.... If you feel that my answer was helpful, please don't forget to use the rating feature as this is we are credited for out time.



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