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115 HP 6 cyl mercury 2 stroke Trim and engine idle problems.

C

CurtisUN

New member
1979 Mercury 115 HP, 6-cylinder 2 cycle outboard.
Understand I took an old 16 ft. Hydra Sports Aero Cobra 120 bass boat to rebuild. I first started the engine, and it ran but would not idle down so i thought ok it is most likely the carbs need cleaning. So, I said I would wait and do that before I take it out because I did not know how long before I got the rest repaired. I then found the trim not working and it was a bad trim pump, so I replace it and got it working. So, I proceeded to rework the boat by putting in new flooring and carpet. I removed and cleaned the fuel tank. While I had the tank out, I replaced the water hoses, recirculating pumps for the live well and the bilge pump.
Last year I put a new trim pump/motor on it and worked it up and down while check the fluid/bleeding air in the up position until it lifted and lowered correctly. It sat for almost 1 year. The trim lowered but will not raise now. Unsure how to proceed. Seen several things about the fluid type. One is to buy mercury fluid which is a oil. (just found this in manual)The manual calls for type A or AF transmission fluid. I used the mercury trim fluid before.
The engine last year would run but at a high idle. I have not been able to start it yet this year but turned it over and tried to start it. But it did not even try. So, I will have to use some starting fluid after I get some to get it to start up.
What I did last year was to retime it, clean the three carbs (which disassembly is not shown in the manual for this carb). The timing was way off to start with. Even the pointer was off. I check compression of all 6 cylinders they were at 95 psi to 100 psi and checked the firing etc. I ran good but just had problem with idle.
Any suggestion would be most appreciated. Thank you
 
I am assuming this is the in-boat pump ? Either way. Check the trim up solenoid, cross the terminals, if it works, replace solenoid.
When you say "did not even try" I assume you checked for spark and fuel and had both, so I'm going to say 90-100 psi is a bit low for this engine. Pump a bit of WD40 into the cyls., the rings might be sticking a bit from lying up.
 
Remove intake bypass covers.----Inspect pistons / rings.----Check for missing bleed restrictors ( if equipped ) as well.
 
haventaclue said:
I am assuming this is the in-boat pump ? Either way. Check the trim up solenoid, cross the terminals, if it works, replace solenoid.
When you say "did not even try" I assume you checked for spark and fuel and had both, so I'm going to say 90-100 psi is a bit low for this engine. Pump a bit of WD40 into the cyls., the rings might be sticking a bit from lying up.
Click to expand...
No, the pump is located in the transom. The solenoids are working, and the pump let it down. But it would not raise it back up. that was incorrect on the compression psi. It had been a year since I had checked it and that psi came from memory and that 90 to 95 was from another engine that I had worked on, and it was a 2 cylinder. I went back to check something in my notes, and it was 120 to 125. So, I could not edit it after I posted. I have not checked the compression this year. But I will recheck it.
I have not had time to do much since I have had a lot of work come up to do.
 
racerone said:
Remove intake bypass covers.----Inspect pistons / rings.----Check for missing bleed restrictors ( if equipped ) as well.
Click to expand...
The compression on this was last year 120 - 125 I posted from memory the 90-95, and I got another engine I was worked on a couple months ago confused with this one and could not go back and edit. It has good compression.
 
CurtisUN said:
1979 Mercury 115 HP, 6-cylinder 2 cycle outboard.
Understand I took an old 16 ft. Hydra Sports Aero Cobra 120 bass boat to rebuild. I first started the engine, and it ran but would not idle down so i thought ok it is most likely the carbs need cleaning. So, I said I would wait and do that before I take it out because I did not know how long before I got the rest repaired. I then found the trim not working and it was a bad trim pump, so I replace it and got it working. So, I proceeded to rework the boat by putting in new flooring and carpet. I removed and cleaned the fuel tank. While I had the tank out, I replaced the water hoses, recirculating pumps for the live well and the bilge pump.
Last year I put a new trim pump/motor on it and worked it up and down while check the fluid/bleeding air in the up position until it lifted and lowered correctly. It sat for almost 1 year. The trim lowered but will not raise now. Unsure how to proceed. Seen several things about the fluid type. One is to buy mercury fluid which is a oil. (just found this in manual)The manual calls for type A or AF transmission fluid. I used the mercury trim fluid before.
The engine last year would run but at a high idle. I have not been able to start it yet this year but turned it over and tried to start it. But it did not even try. So, I will have to use some starting fluid after I get some to get it to start up.
What I did last year was to retime it, clean the three carbs (which disassembly is not shown in the manual for this carb). The timing was way off to start with. Even the pointer was off. I check compression of all 6 cylinders they were at 95 psi to 100 psi and checked the firing etc. I ran good but just had problem with idle.
Any suggestion would be most appreciated. Thank you
Click to expand...
The compression is 120-125. This was a mistake caused by my memory. Sorry
 
haventaclue said:
Check manual release valve and fluid level. Do you have spark jumping 1/4" and fuel?
Click to expand...
I have not had a chance yet to start checking out everything again. I am supposedly retired lol. But since I lost most of my retirement savings back in 2008-2009 crashes, I have had to take some work to make ends meet. I do small engine repairs and electrical/electronic repairs and I had to go yesterday about 50 miles away to repair some electrical problems for a family where that tornado hit here in Mississippi. I have had much more work come in in the last week and have to catch back up if I can lol.
I will get back on it later this week and let everyone know where it stands.
The two main questions I have is how to properly bleed the hydraulics in the tilt system on the transom (the manual is not very clear on this) and what all will cause it start running rough and die when the idle is lowered below 900-1000 rpm. I know about possibility vacuum leaks at carb intake gaskets, also about the idle/higher rpm jets (which these were clean), Which is the first things I will check when I get it started.
What I don't know is what else would cause this idle problem. The engine ran fine at rpms above 900. The timing is to the manual, the carb settings I have tried is every possible way, I have check for fuel pressure and it has 4.5 psi at 1000 rpm but lowers as engine is idle down to 900 o about 4 psi. But these checks were done last year.
 
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