Mercury 2007 Optimax 225HP- Vapor Lock

[Angel]

I have a 2007 Optimax 225HP(s/n OT371401) with what I am sure is a vapor lock issue. It is on a Ranger 520VX. My problem began last year when I decided to try some ethanol free premium gas. I have previously always ran 87 octane. Did not think too much of it. Since then, I have had all the plugs replaced, compressor replaced, the fuel pump rebuilt and fuel filter replaced, water pump replaced, primer bulb replaced. This is my symptoms- first thing in the cool morning, when I punch the throttle, no problem getting on pad. After that, as the weather warms, it take 3-6 times of punching to get it on pad and while priming the new bulb. I even had one day when I could not get it on pad when the weather was over 100 degrees.(I really did not try, I was not that far from the ramp). The engine idles fine, just does not want to get fuel to the engine when I punch it. I suspect vapor lock. Any suggestions on how to resolve this? Any info will be welcomed.

[lpugh]

OE Mercury parts?
Is you bulb laying horizontal in the splash well? If so move it into the bilge out of the direct sunlight and mount it arrow pointed up within a 45 deg angle, Use only a Mercury/quicksilver bulb. Run new Mercury fuel hose from the bulb to the pulse pump eliminating the splice in the rigging tube, be sure to use the correct clamps, it does make a difference
Check the bulb before every start. How many pumps till firm? Need to be sure the VST is full
Then check low and high pressure fuel as well as air pressure with liquid filled gauges while acting up, note the pressures and post them here

[SilverFox579]

Please see the forum that covers your engine.

Mercury - 3 Liter & 3 Liter High Performance

[EuropeanAM]

Moving thread to the correct forum.

[Savage]

Its NOT vapor lock. How many times do you have to squeeze the primer bulb before it gets hard?

[Angel]

6 to 12 times

[EuropeanAM]

Almost certainly a fuel supply problem. Likely that either the pickup tube/anti-siphon valve have problems, previous items were done piece-meal (rather than ALL AT ONCE), something was done WRONG (such as misassembly of the pulse fuel pump), or substandard/incorrect components were used.

See the following link:

FUEL LINES AND PERFORMANCE PROBLEMS

[Savage]

6 to 12 times

Something is wrong between the tank and the VST. I would check the pulse pump and hoses again.

[Angel]

Hi Don,

Thank you for the information. I looked at the fuel line on my boat last night and it is the approved line you suggested, but it has been there since 2007. Should I replace it? Should I replace the splice fitting also?

Thanks,
Angel

[JOE54]

one piece from bulb to pump what I do/ eliminate connection no more leaks

[Savage]

one piece from bulb to pump what I do/ eliminate connection no more leaks

Yep!

[EuropeanAM]

Yes sir- and as suggested, eliminate the splice and run all the way to the pulse fuel pump with the 5/16" Mercury (Gray) line.

I personally would recommend bulb/line be INSPECTED at least ANNUALLY, and also consider replacement of the bulb/line at 5 years.

[Angel]

Thanks for all the insight guys. I 'll let you know how things work out.

[Angel]

Well, I went today and there was no change in performance. engine still not getting gas. while idling today, it died. it has not done this before. I am stumped.

[Savage]

Post #8 has the answer.

[Angel]

I replaced the fuel lines and primer bulb from the VST to the fuel tanks. I also replaced the fuel tank switch valve. I launch the boat in the early morning, prime the bulb, and hit the throttle and it hesitates but it gets up on plane. Go to my first spot and fish a few hours. Get ready to move, prime the bulb again, hit the throttle and it hesitates again a few times but I do get it on plane. Engine runs fine once I get it on plane. As the day gets warmer, the engine will not get up on plane when i hit the throttle and it acts like it is starving for gas. It idles fine. As I was idling to the marina, the engine ran out of gas. I primed the bulb to get more gas to the engine to get going again. The last two trips, the warmer the weather, the worse it got. I am stumped guys. What am doing wrong? Here in Montana, I have not found a knowledgeable mechanic.

[Savage]

If pumping the primer bulb re-fills the VST, then you have a problem PULLING (pumping) fuel from the fuel tank, which is the job of the pulse pump.

Did you rebuild the Pulse Pump?
Did you use Radius head zip-ties on all the hose connections? This is a must to eliminate VACUUM leaks. Do NOT use worm gear clamps.
Did you verify that the fuel tank is venting properly? If air cant enter the tank, then fuel cant leave.
Did you change the fuel filter?

[DewRonInc]

Pulse pump probably issue

[DewRonInc]

Vacuum leak probably one of the diaphrams in pulse pump

[Angel]

Yes to all. It is in the shop now. Looking at the VST and fuel rails.