mariner runs @ 75%

40hp, yr2000, mariner, 3 carbs. won't run at full throttle which is about 4000 rpm's (on my dashboard gage, may be wrong). replaced fuel, cleaned fuel filter, removed carbs and cleaned all ports. If you reduce airflow at full throttle (put hand over intake) it runs up to full throttle. how do you adjust fuel flow to make air intake? it also surges at full throttle.<br /><br />thanks

Re: mariner runs @ 75%

Start looking for an air leak into the engine somewhere. The fuel flow at full throttle (any throttle position for that matter) is controlled by the jetting and the air velocity through the carb venturi. Also check the fuel pump diaprams, they should be changed anually (Mercury's recommendation). If they're a bit old they won't pump enough fuel. <br /><br />Chris.........

Re: mariner runs @ 75%

chris, thanks for the reply. today I took apart the fuel pump looking for debris bit it was clean. The engine is almost five years old and it has never had any work done on it. I guess a rebuild is in order. The jets seem to be clear in the carbs.. I have friends in Sydney and spent some time there doing work for Optus communications back in '91 when it was formed. small world.. I'll get a kit and rebuild the pump..<br />JP

Re: mariner runs @ 75%

Sorry to bust your "small world" bubble, but Perth to Sydney is about he same as LA to NY. Good luck with the fuel pump.

Re: mariner runs @ 75%

Thanks for the help.. rebuilt fuel pump and that did not solve problem. Someone told me that maybe the oil sensor is restricting the engine and preventing it from revving up past a certain rpms. It will run up to 4000 rpm then quickly pull back down to 3200 and then surge sporadically.<br /><br />thanks for any advice..

Re: mariner runs @ 75%

your motor is not affected By oil sensor Or heat alarms as far as guardian.... you Need to find out if it is fuel or ign.. both issues are hard to find on a motor that has a top end issue... for one do you have a restriction.. a fuel presure gauge installed In the fuel line will tell you that .. were looking for 0-3 psi being good.. higher we are restricting... do we have spark On all cyl when the issue occurs .. on way of drop testing a cyl while running is.. we use a small rubber hose with carbon fiber( ibelieve) in the rubber ..atached between the plug & the plug cap( plug cap end has a plug tip Intalled) with all hooked up the mootr willl run.. as if nothing is diffrent.. take a test light ground One end to the motor & touch the rubber hose with the other.. it will drop a good cyl out.. if no drop.. you started to find your problem... a spark test @ cranking is good but this will give you a running test.... picked this tip up in opti school last year.. works great