1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

[X53Gunner]

I bought a boat w/ a 50 merc on it. When I engage the throttle in the idle mode it will rev high into the rpms like a 2 stroke should sound. When I put it in gear and start running the boat it only feels like a 20 hp if that. It sure doesn't sound like it is reving all the way up either. I pulled the plugs and they are not to black and like I said it will rev like crazy when put in nuetral. Not sure what I should check next? Also somtimes will die if run up on throttle for a few minutes, then hard to start and will eventually run back up on throttle then die again. Any help would be great. I have a 84 bass tracker 17' (flatbottom) and wont even come close to plaining out. I believe the 50 merc should plain it right out. Any way let me know what you think!
Scott

 

[jeffdjpeat]

Re: 1984 Mercury 50 HP won't plain out 17' tracker

Re: 1984 Mercury 50 HP won't plain out 17' tracker

is the motor running on all cylinders? and is the fuel pump ok? check those 2 things out. are all cylinders getting fuel and fire? after that im at a loss, unless you need a planer board, but check the motor first.

 

[X53Gunner]

Re: 1984 Mercury 50 HP won't plain out 17' tracker

Re: 1984 Mercury 50 HP won't plain out 17' tracker

Why would it rev like crazy with my nuetral lock out switch engaged and the motor in nuetral but not when in gear. When I put her in gear she might rev a quarter of what it revs when in neutral.
Scott

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

anybody?

 

[CharlieB]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

A weak ignition or fouled spark plugs, either will limit the power output.

Start by testing the spark with an adjustable gap spark tester set to 1/4 to 7/16 gap. You should have a bright blue 'crack', anything less will limit power output while in gear, yet allow 'no load' rpm.

Sooted spark plugs will fire fine at low loads but fail under heavy load.

If it passes the spark test then try a new set of plugs.

If the motor still will not perform correctly then you need to test compression to verify that the motor is mechanically sound.

From there the only thing left is a fuel supply problem, it may be time to spend some quality time with your carbs.

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

I think I might be a dumb *** but I'm not affraid to admit it...LOL I noticed my tank has a vent screw on it and I was running with this closed. I believe it should be open while running. Anyway even with it closed would it rev great in nutraual and then not rev very high in gear? Thanks again for the help!
Scott

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Am I right about the vent and still not sure why it would rev great in nuetral but in gear not rev very high? Thanks again to everyone!
Scott

 

[jeffdjpeat]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

i would give it a shot. loosen the vent and run the motor, it needs to replace the fuel removed with air to run. obviously under a hard load its burning more fuel then at a stand still. give it a shot and see what happens.

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Its been to cold and windy today to put it on the lake. I pulled the plugs to check them out and they are the type of plugs that don't have the arch on the end. Its just the little nub I guess they must be new style plugs. I wonder if they don't arch good enough in the older motor. Or am I just being crazy. Any way thanks for the idea's so far. I'm going to try and put togather a list of what to look at first and run down the list till its fixed. Will take it on the lake this weekend and see what happens. ++++++If someone gets bored and wants to help with a check list of things to try that would be great!!!!!+++++++++ Thanks for your time
Scott

 

[CharlieB]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

The 'surface gapped' plugs are prescribed for a number of outboards.

Are they crusty/sooted up?

Clean the ends with a scotch brite and a little alcohol.

Can you see the white porcelain ring around the center electrode/pin?

If there is too much black glazing carbon from the arcing burning the glass then the plug is about 'fouled', and will not handle heavy loads like lots of throttle in gear. Yet it will rev like crazy in neutral.

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Thanks for the help guys. Here is what I have done so far. I put a new gas line and ball on. I put new spark plugs and fuel filter in the motor. I took it out today and had the tank vent open and my motor never died like it did the first time. (i'm sure due to vent being closed and to much vacum on the fuel the first time out.) It idles great and seems to run great. But when In gear it just doesn't want to rev up. I lock it in nuetral and it will rev to beat the band. I put it in reverse even and it revs higher then when in forward. I might be going 15 miles an hour if I'm lucky with my 17' tracker flat bottom. I won't even come close to planing off. I'm not sure what the check for next? I don't want to bring it to repair man quit yet as I bet someone on here will have a good idea. Thanks again guys for helping with this issue!
Scott

 

[jeffdjpeat]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

hows the compresion?? and hows the fuel pump? the motor uses a lot more fuel and air etc when pushing your boat hard, so running in neutral etc... doesnt mean a lot. maybe clean the carbs while your at it. check compression, then fuel pump, then clean carbs, if your still stuck go see a mechanic.

 

[This_lil_fishy]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

I had the very same problem with an '86 50hp merc. I had to rebuild and adjust the carbs. I was only running on two cylinders. I also replaced the plugs (although the old ones looked okay). I'm certain you'll need a rebuild. Of note, you'll likely have foam floats in the carbs, be sure to replace those and the needles. Should cost less then $100 in parts, but I did them myself, so a mechanic may cost quite a bit to do this job. A good mechanic should be able to do both carbs in less then an hour...two hours tops.

Ian

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Ok sounds like a carb rebuild is due. I was going to rebuild the fuel pump but remembered when on full throttle and doing a big 10 miles an hour...lol I squezzed the ball and it stalled so probably not a pump issue. I'm a motor head as in car and bikes so I think I can tackle these carbs. I don't have a manual can anyone give me a rough start on the adjustments as in fuel/air mixture screws and possible floats. Thanks again to everyone!!!!!
Scott

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

HELP!!!! I pulled the covers off to pull carbs. While in there I noticed a ground wire looks like there are two of them. One is not hooked up. It comes out the the bottom wiring harness. What do you think? Could this have caused all my problems? Should I just hook up the ground button everything back up and go run it? Thanks for the input!
Scott

 

[This_lil_fishy]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

No idea, can you post a pic? Some wires may not be as they seem, if you don't have a tach or temp guage those may be unused harness wires. Tough call.


Ian

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Ok I connected the ground and went for a ride in the boat. It does the same thing. I did notice though as it was late and not alot of people on the lake that after runing for about I would say 10min at Wide Open Throttle the RPM's would climb just a slit bit. No gauge but would gues a few hundred RPM's very slowly. It would seem to hold there Just on the edge of plane but If I went into a turn the RPM's would drop right off back to where they were. Then after awhile climb back up almost gettting me to plan off then turn and would die down. I'm not sure if its fuel related or spark related after this last run. It turns over for awhile before starting but once started she idles fine and runs good, except for at wide open throttle feels and sounds like a quarter a throttle. Let me know what you guys think! Thanks again for bearing with me and my problem child of a motor...LOL
Scott

 

[This_lil_fishy]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

I'm still saying carbs....I'm no expert, and others here are. However your symptoms are very similar to what I experienced. It took me about two days to get everything set just right after rebuilding the carbs, and she ran like a new motor. You may want to change the plugs too while you've got the cover off. They are cheap, and do foul if the carbs are not set right.

Ian

 

[sportsmanphil]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Rebuild your carbs.

Its reving in N easy because there is no load on the motor.

I learned recently that the inlet needles are an issue. My carbs were done last fall and they are already acting up. I was informed that the black tipped inlet needles are crap.

 

[X53Gunner]

Re: 1984 Mercury 50 HP doesn't rev very high in gear and won't plain out 17' tracker

Ok will re-build carbs tomorrow. Will let you know what happens. Thanks again!
Scott