I have a 98 Mercury Marine motor on my 26x that I just bought 5 weeks ago. I had taken the boat out this past weekend after it has been sitting for two weeks. I had trouble starting the engine, it took a couple of starts. Then when it stayed running it ran very rough/irrattic. I had the alarm go off previously and there seemed to be nothing wrong (with oil or water). So we decided to go out after it was warmed up and the alarm had gone off. I shut the engine down and checked everything out and then started it again. It was running but very rough, it was making a chuga chugga sound at low idle (1200rpm). When we got to the bay I was able to open the throttle and it seemed to run smooth. After anchoring for a couple of hours I went to start it and after a few minutes of the engine running it had stalled. Now I couldn't get the motor to start. It was very hard to crank the engine. The battery was at 12volts. After i was towed back to the slip I tried starting it again and it was still very hard to start. I had taken the cover off to access the flywheel and as I was turning the key I would carefully help the flywheel turn and it started and ran but very rough. I noticed that the engine was missing and backfiring from the intake.
I have tried to charge the battery a bit and that did not help. I checked the spark plugs and they seem to have a bit of carbon build up ( i had just chaged them when I bought the boat). I checked the temperature switch and that seems to be working fine. I even tried switching the gas to a higher octane (88 oct)
Has anyone come across this problem or know were to start?
50 Hp Mercury Motor trouble
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Dimitri-2000X-Tampa
- Admiral
- Posts: 2043
- Joined: Fri Jan 02, 2004 5:36 am
- Sailboat: MacGregor 26X
- Location: Tampa, Florida 2000 Mercury BigFoot 50HP 4-Stroke on 26X hull# 3575.B000
Most problems on these engines are caused by fuel supply. Everything from a fuel hose with air leaks (or improperly attached quick fittings) to clogged jets in the carbureter. I would say the fuel system is the place to start.
However, I can't think of too many fuel problems that would cause the alarm to go off. Usually, that would be from overheating, low oil pressure (4-stroke), or in the case of a 2-stroke, no oil in the oil tank.
When I first got my 50HP Merc 4-stroke last year, I found that the PO had twisted the flush fitting around...kinking the internal hose on itself from the twist. Although the motor was still peeing, it wasn't with the full force that it should have had...which could have caused an overheat. I untwisted the hose and the pee pressure went up. From then on, I only use a quick release hose fitting to attach the flush hose and I am very careful not to overtighten it so that the inside fitting starts twisting again. A problem like this could cause your motor to overheat and the alarm to go off. Its an easy thing to spot with the motor cover off.
Best bet is to check the simple fuel line problems first (change the filters too). Use a clear inline filter so you can see what the fuel is doing. The other thing to check is whether there are any big differences between the spark plugs. If one is a lot darker or lighter than the others, it could be a loose spark plug wire or a defective coil...or even worse, a bad valve in the case of a 4-stroke. My PO had left me with a loose sparkplug..which is a good way to burn a valve...but I think I caught it soon enough.
If you have engine mechanic experience, you could go further and check the carbs, compression, magneto, etc. If you don't have the relevent experience, you will likely end up taking it to a shop and spending at least $400. Troubleshooting a 4-stroke is different than a 2-stroke.
However, I can't think of too many fuel problems that would cause the alarm to go off. Usually, that would be from overheating, low oil pressure (4-stroke), or in the case of a 2-stroke, no oil in the oil tank.
When I first got my 50HP Merc 4-stroke last year, I found that the PO had twisted the flush fitting around...kinking the internal hose on itself from the twist. Although the motor was still peeing, it wasn't with the full force that it should have had...which could have caused an overheat. I untwisted the hose and the pee pressure went up. From then on, I only use a quick release hose fitting to attach the flush hose and I am very careful not to overtighten it so that the inside fitting starts twisting again. A problem like this could cause your motor to overheat and the alarm to go off. Its an easy thing to spot with the motor cover off.
Best bet is to check the simple fuel line problems first (change the filters too). Use a clear inline filter so you can see what the fuel is doing. The other thing to check is whether there are any big differences between the spark plugs. If one is a lot darker or lighter than the others, it could be a loose spark plug wire or a defective coil...or even worse, a bad valve in the case of a 4-stroke. My PO had left me with a loose sparkplug..which is a good way to burn a valve...but I think I caught it soon enough.
If you have engine mechanic experience, you could go further and check the carbs, compression, magneto, etc. If you don't have the relevent experience, you will likely end up taking it to a shop and spending at least $400. Troubleshooting a 4-stroke is different than a 2-stroke.
I have the same problem with the flush out connector. The tube spins like you said. I know its not that problem. I whish it was that easy.
My next step is to pressure test each cylinder.
Its possible I am having a couple of issues at the same time. I will check the fuel set up. Do you know if its easy to flush out the jets?
My next step is to pressure test each cylinder.
Its possible I am having a couple of issues at the same time. I will check the fuel set up. Do you know if its easy to flush out the jets?
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Dimitri-2000X-Tampa
- Admiral
- Posts: 2043
- Joined: Fri Jan 02, 2004 5:36 am
- Sailboat: MacGregor 26X
- Location: Tampa, Florida 2000 Mercury BigFoot 50HP 4-Stroke on 26X hull# 3575.B000
I don't know what model you have, but most likely, it is somewhat similar to mine. At the end of last year, a dirty gas tank caused one of my high speed jets to get clogged. Your problem may in fact be the low speed jet(s) if it is running well at high throttle. You have to take apart all four carbs to get to the jets. Its a few hours of work which I wouldn't recommend you take on unless you've done some carb work before.
You can read about my carb problems/resolution here if you want to know more.
Again, with your alarm going off, it may be a more serious problem related to lubrication or overheating.
You can read about my carb problems/resolution here if you want to know more.
Again, with your alarm going off, it may be a more serious problem related to lubrication or overheating.
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Casey
- Chief Steward
- Posts: 86
- Joined: Sun May 02, 2004 9:31 am
- Location: Gulf Coast, MS 98xMerc50hp 2cycle 11.25dia 10pitch 3 blade "Good Winds Karma"
I just went through something similar a few months ago. Here are some quick comments that I remember off the top. If this is a oil injected 2 cycle Mercury 50hp 1998 model:
1. Look at the serial number if you are going to buy parts. You will need this since 1998 was a change year.
2. Put a minimum mixture of two cycle oil in your gas tank to protect your engine in case the oil injector has failed.
3. You can trouble shoot your electricity by checking spark and how it runs with the plug disconnected. My #2 cylinder did not run well but I had spark. You can also check the modulator units by swapping.
4. A simple crack in one of the vacuum hoses will cause it to run rough and drop the top rpm to about 4,000 at wot and flood cough and spit.
5. clogged jets will also cause problems
6. a groove on the needle valve will also cause flooding.
7. I am now a user of stabil when I add gas.
8. If you are going to buy a manual, buy the mercury manual instead of the Hilton's or a generic manual that has many more motors. It becomes confusing.
For mine, a cracked vaccuum hose which I thought was a drain hose, and a groove in the needle valve were the problem. The vacuum leak caused the most problem.
Casey
Good Winds Karma
1. Look at the serial number if you are going to buy parts. You will need this since 1998 was a change year.
2. Put a minimum mixture of two cycle oil in your gas tank to protect your engine in case the oil injector has failed.
3. You can trouble shoot your electricity by checking spark and how it runs with the plug disconnected. My #2 cylinder did not run well but I had spark. You can also check the modulator units by swapping.
4. A simple crack in one of the vacuum hoses will cause it to run rough and drop the top rpm to about 4,000 at wot and flood cough and spit.
5. clogged jets will also cause problems
6. a groove on the needle valve will also cause flooding.
7. I am now a user of stabil when I add gas.
8. If you are going to buy a manual, buy the mercury manual instead of the Hilton's or a generic manual that has many more motors. It becomes confusing.
For mine, a cracked vaccuum hose which I thought was a drain hose, and a groove in the needle valve were the problem. The vacuum leak caused the most problem.
Casey
Good Winds Karma
Casey,
I have a 4 stroke 50HP Mercury Motor.
I'll have to check the needle valves.
I am just starting to get used to working on the outboard. I used to work on cars, so it will take a little studying to get used to it.
You are right about the manual. I boat a generic Mercury manual that has 2HP to 90HP motors. Its a pain to look up stuff and they don't have the correct info sometimes.
Thanks for the info.
I have a 4 stroke 50HP Mercury Motor.
I'll have to check the needle valves.
I am just starting to get used to working on the outboard. I used to work on cars, so it will take a little studying to get used to it.
You are right about the manual. I boat a generic Mercury manual that has 2HP to 90HP motors. Its a pain to look up stuff and they don't have the correct info sometimes.
Thanks for the info.
It could be you still have a plug that is bad even though you replaced them. It could be fouling out at idle. You may have a loose plug.
Is the choke working correctly ?
Seems odd how you moved the flywheel - is the timing off ?
And check around for a reputable mechanic. I also thought I would be out half a grand to get my Suzuki looked at but the complete bill to get my engine running again was not over $150.00 and that included parts.
But.. don't expect someone to get to it fast.
ALso if the have to pull the carbs that could add up fast. My repair didn't require too much part pulling.
Good Luck !
DON B
Is the choke working correctly ?
Seems odd how you moved the flywheel - is the timing off ?
And check around for a reputable mechanic. I also thought I would be out half a grand to get my Suzuki looked at but the complete bill to get my engine running again was not over $150.00 and that included parts.
But.. don't expect someone to get to it fast.
ALso if the have to pull the carbs that could add up fast. My repair didn't require too much part pulling.
Good Luck !
DON B
I finally fixed it....
It turns out the jets on all four carbs were gunked up and had a fine grit on the main jets. I had to take the whole thing apart and clean each carb jets with really small drill bits, thin wire and carb cleaner. It was alot easier than I thought it would be.
After I put everything back together and charged the battery it started right up and purrrrrred. I took it out today for a test spin and it ran like a brand new motor.
The only problem I have is the alarm still goes off when I idle the motor or go really slow. Its the overheat switch that is trigging the alarm. I was feeling the block near the sensor and it would get really hot. If I turned up the RPMs a bit the alarm would go off and the spot would cool off from more water circulating. Does anybody have problems like this ? I haven't looked into it yet. I wanted to get some feed back.
I just want to thank everyone for their input. It was really helpful
It turns out the jets on all four carbs were gunked up and had a fine grit on the main jets. I had to take the whole thing apart and clean each carb jets with really small drill bits, thin wire and carb cleaner. It was alot easier than I thought it would be.
After I put everything back together and charged the battery it started right up and purrrrrred. I took it out today for a test spin and it ran like a brand new motor.
The only problem I have is the alarm still goes off when I idle the motor or go really slow. Its the overheat switch that is trigging the alarm. I was feeling the block near the sensor and it would get really hot. If I turned up the RPMs a bit the alarm would go off and the spot would cool off from more water circulating. Does anybody have problems like this ? I haven't looked into it yet. I wanted to get some feed back.
I just want to thank everyone for their input. It was really helpful
Glad it helped. The first thing I'd do for the alarm is run some weedeater line up the telltale (pee hole) as far as you can go to see if it's partially clogged. It could be the previous owner ran the motor tilted out of the water and burned the water pump impeller slightly. Or it could just be the 6 year old impeller is getting hard and not sealing well any more. Either could cause low water flow at lower rpms, but sufficient at higher rpms.
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Moe
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Moe
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Spirit of the Wind
- Chief Steward
- Posts: 53
- Joined: Wed Jan 28, 2004 6:05 pm
- Sailboat: MacGregor 26X
- Location: Frankford, Ontario
50 Hp Mercury Motor trouble
First off - get the proper service manual. I found it to be well worthwhile. Secondly, if you mess with the 4 carbs, they may have to be rebalanced, which requires a quad vacuum gauge to set up each carb. I opt to have a Merc shop do this since the tester is pretty expensive. As for the overtemp alarm, I've had occasional problems with this. First time I pulled the lower unit and rebuilt the water pump. The kit includes a new impellor, gaskets, etc.
Second time I did the same, but the alarm still went off. Checked the thermostat and overtemp sensor by heating them in a pot of water and both performed as they should. BTW, the service manual says the sensor is normally closed (short ciruit when cold) and opens when overheating occurs. It is actually the opposite. Problem was that the combination zinc/trim tab had broken, allowing water to bypass the auxilliary water intake strainer. After replacing the trim tab, I flushed the motor for over an hour with the motor running and the problem disappeared.
Second time I did the same, but the alarm still went off. Checked the thermostat and overtemp sensor by heating them in a pot of water and both performed as they should. BTW, the service manual says the sensor is normally closed (short ciruit when cold) and opens when overheating occurs. It is actually the opposite. Problem was that the combination zinc/trim tab had broken, allowing water to bypass the auxilliary water intake strainer. After replacing the trim tab, I flushed the motor for over an hour with the motor running and the problem disappeared.
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Dimitri-2000X-Tampa
- Admiral
- Posts: 2043
- Joined: Fri Jan 02, 2004 5:36 am
- Sailboat: MacGregor 26X
- Location: Tampa, Florida 2000 Mercury BigFoot 50HP 4-Stroke on 26X hull# 3575.B000
Actually, I only paid about 50 bucks for a carb synchronizer at JCWhitney. It is made for a 4 cyl motorcycle but works fine with the outboard. The only bad thing is that you have to mess with Mercury (ie, the liquid metal kind, not the motor brand). When I synched mine, I found that the screws were so loose and it took such a slight movement to go back out of sync, that I "glued" them using a silicone sealer and let it dry overnight before running the motor again. It's been idling like a champ ever since...and that is really the biggest drawback of an unsynched engine...won't idle right.