I have a 2007 Mercury 50 HP ELPTO outboard. My last three trips I have had an issue when I go over 1/2 throttle. The motor cranks and idles fine. No issues below 1/2 throttle. Anything above that, the motor bogs down after 10-15 seconds. It bogs down to the point where I come off plane. If I come off throttle and start over, it retains full power for 10-15 seconds and bogs down again. After playing with it to diagnose the issue, I found that if i engage the push key choke when it is bogging down, I can temporarily regain full power for a second or two. If I run and continually push the choke in, it will run wide open with full power, only suffering occasional power loss. If I am running wide open and it bogs down, I can time the choke right to keep it on plane. Obviously this cues me in that I have a fuel issue. I think my first move will be to replace the carbs. Any other thoughts on potential fixes or has anyone suffered from the same issue? All help and input appreciated. For what it's worth, the bulb maintains pressure the entire time.
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Mercury 50 HP Issue above 1/2 throttle
- Thread starter gajet31
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I would take a look at the carbs to see if they just need a good cleaning before you replace them. Make sure the clean the jets good as well. If you can choke it to get your power back, it definitely sounds like some sort of fuel issue to me. I think your right in checking out the carbs first. My motor (1994 Johnson 50/35) was sort of doing the same thing after we rebuilt it. Was fine at idle at lower throttle, but when I'd try to get to WOT it would bog down and not seem to have any sort of power. We neglected to clean the carbs well while doing the rebuild (I blame the beer :beer
. After removing the carbs and giving them a good cleaning, all was well.
. After removing the carbs and giving them a good cleaning, all was well.
Merc Troubleshooting
Could be the carb, see below are some charts from my similar vintage Merc 40hp OB motor. Sound like you are STARVING for fuel, but some OBs have fuel restriction or ‘lean fuel’ alarms (OMC does on V4 & V6 models) but it doesn’t sound like that Merc does.
But here are a few other things I’ve experience directly with OB motors:
Cause – If your fuel lines are old and you’re running ethanol-based E10s fuels, I’ve seen the ID of the fuel lines deteriorate to the point where the OB would run at low speeds, but the vacuum at high speeds pulls the ID of the line shut, as the line is delaminating inside.
Solution[i/] – Running off a separate tank with a different fuel line will prove/disprove this.
Cause – If equipped with an anti-siphon valve on a fixed installation below-deck fuel tank, I’ve seen them clogged up with ‘naval lint’ to the point it limited full RPM operation and/or caused surging at high speeds, especially like after crossing a big wake.
Solution[i/] – If equipped, pull the AS valve and check it. The only place where it would be is right there at the fuel tank fitting connection. It looks like a typical barbed fuel fitting, but inside of it is a SS ball and spring, that gets overcome or pushed aside by the fuel flow. Most times you need to cut the fuel hose to get it off that barb, so you’ll lose an inch or so of fuel line.
Cause – If you had an AS valve and it was clogged, there could crap in the tank, you should then also pull your fuel pickup and check it. Some have a screen on the end, which was intended to protect and keep the AS valve clean/clear/debris free ... but these little screens are fragile and it could either be missing or also clogged up with 'naval lint'. (Nice visual, huh :shock: ?). If missing, I wouldn’t worry about it, less keep an eye on the AS valve for clogging during future high speed ops.
Solution[i/] – The pickups do come out ... mix a 50/50 small mix of acetone and Auto Trans Fluid (ATF) … which is THE BEST penetrating fluid you can get, better than Kroil or PB Blaster and the like. Wipe/weep around threads on boss to the aluminum tank where the square boss is that the fuel barb is stuck into. Use TWO box wrenches 180-degrees apart and with a good oompphhhhh with both hands equally ... and she should spin off easily. Use a good Permatex thread sealant, fuel rated, to re-seat.
Best I can do from cyber-space …
Could be the carb, see below are some charts from my similar vintage Merc 40hp OB motor. Sound like you are STARVING for fuel, but some OBs have fuel restriction or ‘lean fuel’ alarms (OMC does on V4 & V6 models) but it doesn’t sound like that Merc does.
But here are a few other things I’ve experience directly with OB motors:
Cause – If your fuel lines are old and you’re running ethanol-based E10s fuels, I’ve seen the ID of the fuel lines deteriorate to the point where the OB would run at low speeds, but the vacuum at high speeds pulls the ID of the line shut, as the line is delaminating inside.
Solution[i/] – Running off a separate tank with a different fuel line will prove/disprove this.
Cause – If equipped with an anti-siphon valve on a fixed installation below-deck fuel tank, I’ve seen them clogged up with ‘naval lint’ to the point it limited full RPM operation and/or caused surging at high speeds, especially like after crossing a big wake.
Solution[i/] – If equipped, pull the AS valve and check it. The only place where it would be is right there at the fuel tank fitting connection. It looks like a typical barbed fuel fitting, but inside of it is a SS ball and spring, that gets overcome or pushed aside by the fuel flow. Most times you need to cut the fuel hose to get it off that barb, so you’ll lose an inch or so of fuel line.
Cause – If you had an AS valve and it was clogged, there could crap in the tank, you should then also pull your fuel pickup and check it. Some have a screen on the end, which was intended to protect and keep the AS valve clean/clear/debris free ... but these little screens are fragile and it could either be missing or also clogged up with 'naval lint'. (Nice visual, huh :shock: ?). If missing, I wouldn’t worry about it, less keep an eye on the AS valve for clogging during future high speed ops.
Solution[i/] – The pickups do come out ... mix a 50/50 small mix of acetone and Auto Trans Fluid (ATF) … which is THE BEST penetrating fluid you can get, better than Kroil or PB Blaster and the like. Wipe/weep around threads on boss to the aluminum tank where the square boss is that the fuel barb is stuck into. Use TWO box wrenches 180-degrees apart and with a good oompphhhhh with both hands equally ... and she should spin off easily. Use a good Permatex thread sealant, fuel rated, to re-seat.
Best I can do from cyber-space …
Attachments
Watch the fuel filter while it's running to see if it drops down until it's almost empty or for air bubbles possibly getting in. My fuel line to motor fitting seems to come loose from time to time and last weekend I started getting a bad bog and it turned out air was getting in. I could see the filter drain down and the air coming through. I disconnected the fuel line and noticed an air bubble on the o-ring so I seated it all the way and plugged it back in and it's fine. But watching the fuel filter might give you an idea if it's not getting enough fuel if it drops down when running.
