'96 Mercury Force 75 stalls but only in the water!

[wolverine9827]

Hi All,

Color me thoroughly confused...

Background: I have a 21' pontoon with a '96 Mercury Force 75 3 Cylinder. Early on I had problems with the starter bendix popping up and I replaced the bendix.. The motor would start (I still had to manually pop the bendix up at times) and ran pretty well... Being a boat engine newbie, I was completely ignorant of ethanol and of stabilizers and one day on the way in the motor kept stalling.... but once back at my lot, I could hook it up to water flush it and it would run without any problems at all. It sat for a month or two and some friends advised me to putting some stabilizer in the fuel. I added a hair more than what was listed for a 24 Gallon tank and then mixed up the fuel with a little extra oil. I replaced the plugs, plug wires, and fuel filter and also replaced the entire starter and also drained and refilled the gear case lubricant. Now it starts rights up and I can rev it and it roars like a champ! I can then put it in gear and also rev it up without any problems and the prop turns as expected. One thing I did notice while both throttling up in neutral or in gear was that when the throttle was quickly brought back to an idle, it sounded like the engine skipped and "twitched" while the rpm's came back down to a smooth idle. Standing at the engine I could rev it above the throttle cable's ability and it would rev up without hesitation. The "sound" of the engine while revving up in the high rpm's is a bit scary with me standing right next to it and being a bit of a newbie I am hesitant to rev it up too high... With that being said, I can only describe the engine's sound as a "not quite skipping but not an entirely smooth, low throated roar that at the top of the rpm high end (as far as I nervously dare to push it) it sounds as though it could rip itself apart and take me out with it! Whether it actually would do this is doubtful, I'm just a bit nervous with the sound of this roaring beast and it's only a 75 HP!... Water is pulled into the engine and comes out the drainage hole in a steady stream. The exhaust is a slight bluish tinted grey color.

Now the problem: I can hook it up to the water intakes and fire it up and rev it all day both in neutral and in gear and it roars like a champ. No stalls, no issues. However, as soon as I put it in the water, I can't go faster than a 7 mph putz without the engine vibrating and then stalling. Once it stalls it won't start for a few minutes. If I put it in reverse and rev it in any kind of fashion it immediately stalls - no vibrations, just an immediate cut out. Again, it will take a few minutes before it is able to start again. If I just put it in gear and let it go, it can putz all day. In forward, I can give it a little throttle and it will respond without hesitation and go without a problem but if I throttle up from there it will start to vibrate and this will worsen until it coughs and stalls. Taking it back to my lot, I can again hook it up to the water intakes and it will throttle up fine whether in gear or not.... I am guessing that this is telling me at least two things:

1) The Fuel system is fine (fuel filter, carburetor, and fuel pump, wires, plugs, etc...)
2) Since the engine only stalls while under a load, the problem is related to the lower assembly somewhere.... gear case or prop shaft or something.... but not bad enough to exhibit any symptoms when the prop is "clear"

I did notice one thing: There are two bolts at the 12 and 6 o'clock positions at the prop cuff (? - on the lower unit but not the prop itself)... the bottom bolt appears to be seeping oil. I've attempted to tighten it thinking it was loose but it's tight. It doesn't leak much, but enough for me to notice the dark coloring and some wetness on the bolt. I'm half afraid to loosen either of those two bolts fearing that the entire inside will spring out in a shower of gears and stuff leaving me to figure out how to piece it all back together again!

I don't know where to go from here and I can't afford to just take it in and have a real mechanic pull it apart and do whatever needs to be done. I'm not cheap or anything - I just don't have the money! I've been piece mealing this baby together doing what little I know how to do and learning on other things as I go. I have a fuel pump rebuild kit but haven't tackled that one as of yet since it doesn't appear to be a problem that I can tell.....

Does anyone have advice on what I should do next? Please bear in mind that I'm an engine (especially boat engine) noob.... I'm at the end of my knowledge (which isn't much) and I would greatly appreciate any and all ideas. 75 HP is pretty much a waste if I can only go 6 mph!

Thanks all. I apologize for the size of this post.

Wolverine

 

[maxum00722]

Re: '96 Mercury Force 75 stalls but only in the water!

Hi All,

Color me thoroughly confused...

Background: I have a 21' pontoon with a '96 Mercury Force 75 3 Cylinder. Early on I had problems with the starter bendix popping up and I replaced the bendix.. The motor would start (I still had to manually pop the bendix up at times) and ran pretty well... Being a boat engine newbie, I was completely ignorant of ethanol and of stabilizers and one day on the way in the motor kept stalling.... but once back at my lot, I could hook it up to water flush it and it would run without any problems at all. It sat for a month or two and some friends advised me to putting some stabilizer in the fuel. I added a hair more than what was listed for a 24 Gallon tank and then mixed up the fuel with a little extra oil. I replaced the plugs, plug wires, and fuel filter and also replaced the entire starter and also drained and refilled the gear case lubricant. Now it starts rights up and I can rev it and it roars like a champ! I can then put it in gear and also rev it up without any problems and the prop turns as expected. One thing I did notice while both throttling up in neutral or in gear was that when the throttle was quickly brought back to an idle, it sounded like the engine skipped and "twitched" while the rpm's came back down to a smooth idle. Standing at the engine I could rev it above the throttle cable's ability and it would rev up without hesitation. The "sound" of the engine while revving up in the high rpm's is a bit scary with me standing right next to it and being a bit of a newbie I am hesitant to rev it up too high... With that being said, I can only describe the engine's sound as a "not quite skipping but not an entirely smooth, low throated roar that at the top of the rpm high end (as far as I nervously dare to push it) it sounds as though it could rip itself apart and take me out with it! Whether it actually would do this is doubtful, I'm just a bit nervous with the sound of this roaring beast and it's only a 75 HP!... Water is pulled into the engine and comes out the drainage hole in a steady stream. The exhaust is a slight bluish tinted grey color.

Now the problem: I can hook it up to the water intakes and fire it up and rev it all day both in neutral and in gear and it roars like a champ. No stalls, no issues. However, as soon as I put it in the water, I can't go faster than a 7 mph putz without the engine vibrating and then stalling. Once it stalls it won't start for a few minutes. If I put it in reverse and rev it in any kind of fashion it immediately stalls - no vibrations, just an immediate cut out. Again, it will take a few minutes before it is able to start again. If I just put it in gear and let it go, it can putz all day. In forward, I can give it a little throttle and it will respond without hesitation and go without a problem but if I throttle up from there it will start to vibrate and this will worsen until it coughs and stalls. Taking it back to my lot, I can again hook it up to the water intakes and it will throttle up fine whether in gear or not.... I am guessing that this is telling me at least two things:

1) The Fuel system is fine (fuel filter, carburetor, and fuel pump, wires, plugs, etc...)
2) Since the engine only stalls while under a load, the problem is related to the lower assembly somewhere.... gear case or prop shaft or something.... but not bad enough to exhibit any symptoms when the prop is "clear"

I did notice one thing: There are two bolts at the 12 and 6 o'clock positions at the prop cuff (? - on the lower unit but not the prop itself)... the bottom bolt appears to be seeping oil. I've attempted to tighten it thinking it was loose but it's tight. It doesn't leak much, but enough for me to notice the dark coloring and some wetness on the bolt. I'm half afraid to loosen either of those two bolts fearing that the entire inside will spring out in a shower of gears and stuff leaving me to figure out how to piece it all back together again!

I don't know where to go from here and I can't afford to just take it in and have a real mechanic pull it apart and do whatever needs to be done. I'm not cheap or anything - I just don't have the money! I've been piece mealing this baby together doing what little I know how to do and learning on other things as I go. I have a fuel pump rebuild kit but haven't tackled that one as of yet since it doesn't appear to be a problem that I can tell.....

Does anyone have advice on what I should do next? Please bear in mind that I'm an engine (especially boat engine) noob.... I'm at the end of my knowledge (which isn't much) and I would greatly appreciate any and all ideas. 75 HP is pretty much a waste if I can only go 6 mph!

Thanks all. I apologize for the size of this post.

Wolverine

I'm new to this site so I hope I'm doing this right! I'm not a mechanic, but from what I understand a stotor, which is under the flywheel is kind of like a coil. I think it produces initial spark for the rest of the system?

 

[CharlieB]

Re: '96 Mercury Force 75 stalls but only in the water!

Don't rev the motor unloaded, to high too long and it WILL grenade.

Ring-ding-ding is normal for an unloaded 2 stroke slowing from high unloaded revs, don't do that anymore, OK?

Now, unloaded a motor with a dead cyl OR a lean idle mixture will rev fine, yet once in the water is a complete flop. The trick is to figure out which and deal with what you need to to protect the motor from destroying itself.

Check for a hot blue spark on each cyl that will arc blue fire across a 7/16 inch gap. Chances are all may be fine, if so then move onto the carbs. If not repost and we'll get into Igniton Troubleshooting.

Old fuel, carbs left un-used for long periods, contribute to small idle passages getting restricted from oil/crud deposits, causing the idle mixture to go lean. The proper fix is to order carb kits (cheap enough), clean and readjust all carbs, paying critical attention to the idle mixture screws and the float levels.

Not recommended but...... Gently turn each idle mixture screw in till it is LIGHTLY seated, COUNT the exact # turns and write it down so that you can put it back exactly once finished. Remove the screw and stick the 'lil red tube on a can of Wal-Mart Super Tech Carb Cleaner in the hole and give it a 4 - 5 second shot, wear glasses just in case it sprays back at you. Remove the carb bowl drain, pump the primer bulb and flush everything out with fuel. Reinstall the drain and the idle needle to the exact original # turns out from lightly seated.

Repeat on all carbs.

If motor performance is not perfected, remove the carbs for total proper cleaning.

 

[wolverine9827]

Re: '96 Mercury Force 75 stalls but only in the water!

Don't rev the motor unloaded, to high too long and it WILL grenade.

Ring-ding-ding is normal for an unloaded 2 stroke slowing from high unloaded revs, don't do that anymore, OK?

Now, unloaded a motor with a dead cyl OR a lean idle mixture will rev fine, yet once in the water is a complete flop. The trick is to figure out which and deal with what you need to to protect the motor from destroying itself.

Check for a hot blue spark on each cyl that will arc blue fire across a 7/16 inch gap. Chances are all may be fine, if so then move onto the carbs. If not repost and we'll get into Igniton Troubleshooting.

Old fuel, carbs left un-used for long periods, contribute to small idle passages getting restricted from oil/crud deposits, causing the idle mixture to go lean. The proper fix is to order carb kits (cheap enough), clean and readjust all carbs, paying critical attention to the idle mixture screws and the float levels.

Not recommended but...... Gently turn each idle mixture screw in till it is LIGHTLY seated, COUNT the exact # turns and write it down so that you can put it back exactly once finished. Remove the screw and stick the 'lil red tube on a can of Wal-Mart Super Tech Carb Cleaner in the hole and give it a 4 - 5 second shot, wear glasses just in case it sprays back at you. Remove the carb bowl drain, pump the primer bulb and flush everything out with fuel. Reinstall the drain and the idle needle to the exact original # turns out from lightly seated.

Repeat on all carbs.

If motor performance is not perfected, remove the carbs for total proper cleaning.

Awesome info! Thank you so much for the advice! I will definitely be more careful with revving the engine from now on.

I feel kind of dumb asking this.... but... how do I check for that hot blue spark on each cylinder?
Wow, now I really realize how much I don't know... like how to remove the carb bowl drains or even the carbs in general including the needles (?) I thought the big grey metal piece at the boat side of the motor was the carburetor... is that just the air intake and the carburetors are behind it? I had sprayed the above mentioned Carb Cleaner stuff into what I guess now is the air intake... Gave it a good spraying down and let it air dry for 10 minutes or so then started up the motor and sprayed 5 or 6 short bursts down its throat... Hope I didn't hurt anything... the engine had stalled at that point but started right up again.... I'm paranoid about damaging something beyond repair so I try to be extremely careful and conservative.... I now have some research to do on how to remove, clean, reassemble, and adjust the carbs and what a float is and these needles... and what is even used to clean carbs with (other than the spray that I already have)... lol... Thanks for all you help.

Once I know how to check for spark I'll repost with the results and go on from there....

Thank God for those that know this stuff!!

 

[wolverine9827]

Re: '96 Mercury Force 75 stalls but only in the water!

Thanks maxum... I think I know what part you're talking about... the stationary piece under the spinning gear thing on top (the fly wheel?) - The Fly wheel has magnets that rotate in close proximity to the stator's magnets and coils producing voltage and together these two pieces act like an alternator on our cars... right? charging the battery(ies) ... so in your case, replacing the stator didn't initiate the need for adjusting the timing, it was the removal and re-assembly of the flywheel (I'm guessing based on other posts I've read and my own attempts to learn how these outboards work)... at least I'm hoping I am understanding that right..... at least now I know what that thing is that is sitting under my flywheel (on mine it's red and is quite clean for it's age) - Thanks for that