1985 50 hp mariner no speed

[srussell28]

I have had nothing but problems with this motor for the last year. I can get only 7-10 mph. I have rebuilt the carbs 2x, new starter, rectifier, spark plugs and wires, stator, battery, water pump, tank, bulb and fuel line, fuel filter is clean. Get 130, 130, 130 128 psi on the cyl. Check all the wiring, can't find any bad. Sounds great out of the water, in the water it goes up to about 1/2 to WOT the no more speed. The boat is not water logged it's 16 ft ski barge that I can move on the trailer with my hands, so It's not heavy. Thanks for any help anyone can offer.

 

[srussell28]

Re: 1985 50 hp mariner no speed

I have also switched the coils around, and can pull each spark plug wire and hear the diiference. I can also cover each carb with my hand and make it almost cut off on each one.

 

[studlymandingo]

Re: 1985 50 hp mariner no speed

Everything good with your lower unit? Fluid clear, not milky, no shavings?

Also, in your list of repairs, I did not see fuel pump, if you pump the bulb while it's bogging, does it pick up RPMs?

 

[srussell28]

Re: 1985 50 hp mariner no speed

Everything good with your lower unit? Fluid clear, not milky, no shavings?

Also, in your list of repairs, I did not see fuel pump, if you pump the bulb while it's bogging, does it pick up RPMs?

 

[studlymandingo]

Re: 1985 50 hp mariner no speed

What is your prop pitch? Since you have owned this motor, has it ever planed out?

 

[srussell28]

Re: 1985 50 hp mariner no speed

Yes I have checked it, no shavings, fluid changed last year, and checked it last week looks good, not milky. The fuel pump is on the carbs right? I have wma3-1 and wma 3-3 carbs. When it bogs down the RPM's never go up. I just ohmed the stator and trigger both are in range. Going to check the coils now. Thanks for the help.

 

[srussell28]

Re: 1985 50 hp mariner no speed

when I first got it two years ago I could only get up to 20 mph. End of last year it started with this issues

 

[srussell28]

Re: 1985 50 hp mariner no speed

the prop is quicksilver 48 762030 as 14p. I s that ok for this 85 50hp?

 

[srussell28]

Re: 1985 50 hp mariner no speed

Yesterday I noticed that all the plugs are getting wet, but can't see where the water is coming from. Could this be the issue?

 

[fishingdan]

Re: 1985 50 hp mariner no speed

Are you absolutely sure that you have good spark to each cylinder? I have the mercury sister of that engine (same engine) and know that it will run like that when it is running on 2 of 4 cylinders. In neutral or running on the muffs out of the water, it can be difficult to hear the difference and she will freely rev (although you don't want to do that). With 2 of 4 cylinders firing, it will have a max rpm of around 2500 rpm.

It would be very common for you to be at the point where the switch box needs to be replaced (the electronic box on the side of the engine). When they start to go, they can cause intermittent problems. For example, when my engine was cold it would run on all 4, but then drop 2 as it warmed up.

 

[srussell28]

Re: 1985 50 hp mariner no speed

What is the best way to check for spark. I can pull each plug and hear the difference, I can also get spark to the block by taking the lplug wire off. Thanks for any help. Will the DVA help check the spark or the coils?

 

[fishingdan]

Re: 1985 50 hp mariner no speed

You can pick up an inexpensive spark tester at any autoparts chain. These are less than $10.

 

[srussell28]

Re: 1985 50 hp mariner no speed

I got a spark plug tester and the motor is getting good spark. I also just got a DVA how do I test the power pack, or what do I need to check now?

 

[srussell28]

Re: 1985 50 hp mariner no speed

I also checked the coils, trigger and stator all were in the specs.

 

[srussell28]

Re: 1985 50 hp mariner no speed

I was double checking the spark Just now, and 1 & 2 DON'T FIRE as fast as 3 AND 4? Could both the coils 1 & 2 be BAD? I checked the ohm and they are in the specs? Please let me know what else I can do. Thanks.

 

[fishingdan]

Re: 1985 50 hp mariner no speed

Unfortunately, I don't know how to test a power pack. I do know, based on my experience, that when they start to go, they cause sporadic issues and the issue always seem to affect 2 cylinders at a time. If I recall, there is one coil for each cylinder. This would imply to me that a bad coil would only impact one cylinder.

IOn one bad power pack that I had, it would run ok on all cylinders for the first 20 minutes or so and then it would drop two cylinders. While troubleshooting, I started to get frustrated because I couldn't figure out how to test the powerpack. While the engine was running, I banged on the power pack with a screwdriver and the engine took off. When I stopped, it dropped 2 cylinders again.

 

[srussell28]

Re: 1985 50 hp mariner no speed

Thanks Fishingdan, I did find this morning that the Hub had moved from where I had marked a few weeks ago. I just got that fixed today. As I read in other forums some people say that "The top 2 coils don't and pickup til it gets to higher RPM. Do you think that this is true?

 

[srussell28]

Re: 1985 50 hp mariner no speed

well I spent 570, new power box, new tach, wiring, new plugs, new rectifier, and nothinhg has changed. Were are the pros? Why do people read the post but don't reply? The subject says it all. Also new stator and 1 carb.

 

[srussell28]

Re: 1985 50 hp mariner no speed

Today I tried another gas tank and fuel line with bulb, and guess what. the JET, ECONOMIZER(.098) is shooting gas out of it. Why is this happening?

 

[Hitman]

Re: 1985 50 hp mariner no speed

I am far from an Expert, on Mercury,Mariner , and your problem is spreading. I had a Tracker 17 pro come in with a 45 hp Mariner, same as the 50 , that will not turn over 2000 rpm's on the water. It has a new Stator( it was bad) and have tried a trigger, switchbox, carbs disassembled and checked, fuel pump diaphram replaced, and ran on a shop tank with good gas and oil. It act's like a stator bad, but the rectifier has also been changed. I think we have found a problem with these motors possibly brought on by the fuel companys maybe changing the gas. I have no clue that's why I'm asking for help. Merc tech support is no help, they say motor is to old. Any body? Thanks
Tom