2002 Mercury 50hp 4 stroke (bigfoot) help

[flttech]

Newbie here. I have a 15' Sylvan deep Vee aluminum fishing boat with a 2002 50hp Bigfoot fuel injected motor on it. I purchased the package new back in 2003 so they were already mated up. Since then I have figured out that the Bigfoot was really designed for pontoon boats but I'm stuck with it. Now for my question/problem. My boat is fairly light, I believe with engine it should be around 1200lbs. It came with a 17 pitch prop but the performance was sluggish at best. I had a tach installed and found out the rpm's at wot were 4800. The dealer installed a 13 pitch to get me just up to 5500, the bottom of the recommended range of 5500-6000. Now if I go on to Mercury's website and use their prop locator it gives me an error when I punch in my data as being outside expected values. The boat does 29 mph as verified by my onboard gps. My question is whether the engine is running the way it should as far as power goes. I've always suspected it runs out of fuel up top. The pressure at the fuel pump on the motor is 44 psi though. The only confusing thing is that at idle I don't have any fuel in the bulb with the filter. Just a trickle at the bottom. I can pump the bulb full with the fuel bulb on my line but it slowly drains back down. The other thing is that the throttle was not adjusted to open all of the way with the throttle at the console. I was able to adjust quite some more and visually confirm that the linkage was being actuated on the motor. However, when I take it out on the water, that extra movement of the throttle doesn't result in any increase in rpm. My 2 questions are should my fuel bulb with the filter in it on the motor fill up at least partially at idle, and do these perfomance numbers for my boat sound in the ballpark? Any suggestions would be appreciated. I've changed both fuel filters/plugs/ and fuel lines going to the motor

[boats.net]

It sounds like it's running in range. The primer bulb wont stay hard when running and it's not uncommon for fuel filter to not stay full, fuel simply just pass through it.

[flttech]

I agree, however, my fuel bowl with the filter doesn't fill up at all. you can see a small trickle in the bottom but no fuel accumulates at all. When my high pressure pump was checked it read 44psi (or so the mechanic checking it claims as I was at the key). However, his fuel pressure guage fittings were spraying fuel all over the place. He estimated 50psi without the leaks but I wont know until I get a good gauge from somewhere else. I'm thinking right now that with a good gauge which I will have to find that the pressure is probably higher than the alloted 44psi. I did change spark plugs and noticed they were wet but moved on to other things and let it slip my mind. I'll pull the new plugs and check if they're wet too. My thoughts over the last 24 hours are that the low pressure fuel pump is doing it's job fine and that the high pressure pump has gone well above 44psi. That could explain why the fuel is all but not visible in the bowl as it's getting sucked out faster than it can be replaced. My idle is also 900rpm vice the 725 in the manual. The bottom line is that to get this motor in the middle of the operating range I would need to drop down to an 11 pitch prop and I just can't accept that since it's on such a light boat. The dry weight of the boat without engine is 560lbs. I will find the problem but it may take a year or two! I just wish there was someone with a Bigfoot or even normal 50hp 4 stroke that could look at their fuel bowl at idle (while they were flushing their motor) and let me know what if any fuel level they had in there. As I was saying there is no fuel visible in mine unless you look in the very bottom and can just see a trickle

[TMD]

It is normal for the fuel filter to trail off and become low as the engine is operating.

You have a clue with your RPM at idle.

The ECM is designed to raise the RPM should a sensor not be operating within proper spec's. This is to keep the engine running and alert a Tech that there is a problem.

Does your Tech not have a DDT or a Laptop to test the engine?

http://www.themarinedoctor.com/cgi-bin/YaBB.pl

TMD