1970 merc 115 hp inline 6 problems

[nate712]

I have a 1970 merc 115 hp inline 6 2 stroke serial #28xxxxx when i first bought the boat it would run great until you ran at wot and backed off it then it would bog down and not run wide open again for hours. I changed the fuel pump diaphrams, rebuilt and cleaned the carbs and spark plugs in the process of removing the top carb i had to loosen the distributor now it will hardly run and none of the "stops" ie. max spark advance etc are nowhere close to the distributor. Ive followed the very vague process in the manual to synchronize everything but the distr. just doesnt seem to be anywhere close to where it should be, the manual says 5-7degrees btdc and at idle its at about 25-30. any ideas or tips on adjusting the distributor would be greatly appreciated im at the point of buying a used good running engine!!

 

[Chris1956]

Re: 1970 merc 115 hp inline 6 problems

An OEM manual has the exact procedure to time that motor. Here is how I time my '77 Inline 6.

Set the top cylinder to top dead center(TDC), using a screwdriver. Your motor should have a timing mark on the cowl support. See that it matches. Now remove the distributor cover pulley, and make sure the cast in arrow points to the punch mark on the flywheel. If not slip off the timing belt and make is so. Renstall the cover + bolt with a bit of locktight.

Now remove all but #1 spark plugs and install them into their wires. Tape them together and ground them. Install timing light on #1 plug wire(on spark plug). Crank motor and set throttle to show 4-6*BTDC. Stop cranking and loosen two 5/16 bolts on midsection of distributor and rotate collar until it just touches carb lever on top carb. Tighten bolts. Carbs should just start to open at 4-6* BTDC. Now advance throttle to maximim. Crank motor and turn max spark advance screw until max advance is 21* BTDC. Tighten lock nut. Now set throttle stop screw to allow carbs to open almost to the carb stop, and tighten locknut.

Install spark plugs and run motor on flusher. Set idle speed to 900-1000RPM and adjust idle stop screw to hold it there. You may need to adjust throttle cable to make it so.

 

[64osby]

Re: 1970 merc 115 hp inline 6 problems

Chris1956. That was a nice explaination. Would the same process also apply to a 1967 500 Merc. ?