1984 115HP Mercury No Power

[CTuck1002]

New boat owner and member to the site. Recently bought a boat for a few hundred bucks from a buddy in my company. Has a 1984 Mercury 2 stroke in line 6 cylinder. Serial number 6479646. The engine will start and idle but really doesn't have any power. Buddy replaced the spark plugs with Champion plugs (wrong ones according to your site) and lower CDI. He said that the oil pump was bad and needed to be ran with a pre mixed fuel and later found out was running way too much oil (like 200 or 300:1 ratio) adjusted the carbs so it would half way run with that mix. I haven't had a chance to do any basic test like compression or spark because I've been out of town. I need to know where I can find acceptable specifications for that engine. I pulled the plugs and the top three were soaked in oil the bottoms three, not so much. Appears that someone had recently went through the engine because of red RTV on pretty much all the visible gaskets. The engine will run and have taken it out three times just to try and see what's going on with it and to do minor repairs to the trailer. If I have good compression on all cylinders what's my next step and what's an acceptable psi range?

Thank you all in advance for any advise given.

 

[racerone]

Well, a 200:1 or 300:1 ratio is not nearly enuff oil !!!------------Should be 50:1-------Do the math.

 

[Chris1956]

Compression should be within a 15% variation across all cylinders. Gauges are often inaccurate, so if the variation is acceptable the compression is fine. Check for spark on all cylinders. I suspect you only have spark on the bottom 3 cylinders.

A 300::1 fuel mix is 1/6 of the normal oil. If that is truly what you have, add 5/6 more oil. You want 1 pint oil for 6 gallons of regular gasoline, for a 50::1 mix.

 

[racerone]

One switch box fires #1 , 3 , 5----The other fires # 2 , 4 , 6 on these motors.

 

[CTuck1002]

Once this tropical storm passes I'll check for spark and compression. My apologies with the incorrect ratio... Just meant that he was adding too much oil to the fuel like 2-3 quarts per 10 gallons is what he told me. Ill take a look at the CDI boxes again but it looked when I chased the wiring that the top box is wired for the top three cylinders and the bottom for the bottom three. If that's incorrect then I do need to correct that but I wouldn't think it would even idle with the ignition out that much.

 

[racerone]

??----One CD box fires cylinders #1 , 3 , 5 ----the other box fires #2, 4 , 6 ------But check the online wiring diagrams if you still doubt this fact.