1979 115hp Mercury in-line6 - runs rough

[Jim Berry]

I have a 17ft runabout with a 1974 evinrude 85hp motor(ran perfect). I am a waterskier and decided to get a 115hp Mercury which I thought was a 1986 and turns out to be a 1979. I saw the motor run with ears on and actually put it in gear for about 2-3 minutes, which after reading the manuals, was a big NO-no. Anyway. I got the motors swapped and took the boat with the mercury engine to the lake. After a lot of cranking it finially fired-up and I actually took it out for a spin. Been out 3 times and it runs
rough and actually i could not get it to fire the last time I went out. Do you think I damaged the motor by running it in gear? From what I have been reading, I am sure the carberators need to be worked on.
My wiring harness is not in very good shape either. Where is the best place to purchase a new wiring harness? Anybody know a good boat mechanic in Charlotte, NC I know compression on the motor is good. Knowing that, I am assuming motor can be fixed. Should I put money into this motor?

 

[mr 88]

Re: 1979 115hp Mercury in-line6 - runs rough

Better response in the Mercury/Mariner forum.How new are the plugs? These motors can be finicky when starting.Try priming the bulb until its hard then put neutral idle control all the way up.Hit key and choke button at the same time . No I do not THINK you damaged the motor when you put it in gear.I would buy some Sea Foam from NAPA/Wally World etc and put initially put in 2-3 times what they call for into your 6 gallon gas tank. Then I would put some into a spray bottle and when in the higher speed idle mode spray into the carbs direct until it sputters. That MAY clean up your carbs without having to pull them off.Yes that is a good motor worth putting some money into especially if the compression is even and good.Wiring harness can be found on Ebay or re wire it yourself.

 

[Jim Berry]

Re: 1979 115hp Mercury in-line6 - runs rough

Thankyou for the reply. I think I can handle that, even though I am not very mechanical. Trying to fix all the simple thinks first. I did change the plugs and the gas line. Sometimes it just clicks when I start instead of turning over. I just got a starter solenoid hoping that will fix that problem.
You made my day (something else to try) - Thanks

 

[Gomer50]

Re: 1979 115hp Mercury in-line6 - runs rough

This where I purchased mine.
http://www.outboardparts.com/mercury/mall/merchrnss.htm

 

[Jim Berry]

Re: 1979 115hp Mercury in-line6 - runs rough

This where I purchased mine.
http://www.outboardparts.com/mercury/mall/merchrnss.htm

I got bigger problems. I started looking at all the wiring and it is in bad shape. I will need to get a new internal wiring harness. The wire to my capacitor broke when I touched it. I think I found my problems.
Saw new harness on Ebay for $110.00 at CC Marina in South Carolina. Sounds like a bargin to me.
Has anyone seen anything better ?

 

[Jim Berry]

Re: 1979 115hp Mercury in-line6 - runs rough

Got motor running. Noticed I had water in the lower unit. Pulled the lower unit last weekend Found seal on the bottom side of pump was bad. Got unit back together. The Seloc manual showed piece by piece what to replace as far as the water pump etc... I am told that there are only 2 -ways water can get in the lower unit.
1st - around the water pump & 2nd down by the prop. If I put the rabbit ears on and run at home, that should tell me if my seals are good or bad around the pump. Just need to check the oil and make sure there is on water in it. So if I am good there, then water must be coming in around the prop. Pulled the prop, then there was a big metal washer pulled-off, then your looking into the enclosed area that looks like there is a metal bushing with a rubber seal. The seloc manual does not show any detail on this. Any ideas were I can get more detail on this ?? I bought a seal kit and I don't think i have the right stuff for this part of the motor. Is there anything on-line to look at ?

 

[gwukena]

Re: 1979 115hp Mercury in-line6 - runs rough

Got motor running. Noticed I had water in the lower unit. Pulled the lower unit last weekend Found seal on the bottom side of pump was bad. Got unit back together. The Seloc manual showed piece by piece what to replace as far as the water pump etc... I am told that there are only 2 -ways water can get in the lower unit.
1st - around the water pump & 2nd down by the prop. If I put the rabbit ears on and run at home, that should tell me if my seals are good or bad around the pump. Just need to check the oil and make sure there is on water in it. So if I am good there, then water must be coming in around the prop. Pulled the prop, then there was a big metal washer pulled-off, then your looking into the enclosed area that looks like there is a metal bushing with a rubber seal. The seloc manual does not show any detail on this. Any ideas were I can get more detail on this ?? I bought a seal kit and I don't think i have the right stuff for this part of the motor. Is there anything on-line to look at ?

Get a proper merc manual, goes into detail, shows proper tooling needed. If you can't make up tooling, best to take it to a shop for reseal.

There's more than two spots for water entry.

1. Water pump housing and associated seals, if lip seals/housing bad, the housing from merc comes with lip seals already installed. Be aware if your driveshaft does not have a preload pin, the water pump housing sets driveshaft upper bearing preload and will have to be shimmed accordingly if housing replaced.

2. Prop shaft seals and carrier o-ring.

3. Shift shaft bushing and seals.

4. Lube fill and vent screw gaskets

As far as checking on the muffs, may not tell you anything. The lower unit needs to be pressurized and checked for leaks. It also needs to be put under vacuum and checked. I would replace fill and vent screw gaskets first, if not already done.

 

[Jim Berry]

Re: 1979 115hp Mercury in-line6 - runs rough

AS stated before - had replaced all the seals around the water pump. Took the boat out
this weekend and ran for 1-hour, came home and checked the lower unit again - more water.



Its got to be coming in around the prop. After looking at that area, Not sure where to start.

Does everyone else agree that this is a tough job for the non-experience boat mechanic like me?

I would think that this would be no more than $200.00 for the experienced boat mechanic