Mercury 115, Vintage 1976, Starter/Ignition Trouble

[Rob Koller]

Great forum,<br /><br />I just joined, been reading up on the Mercury 115, and I just ordered a maintenance /repair manual from iboats.com for this Mercury 115.<br /><br />I thought I would post my engine issue to see if there is some experience out there on where to begin. Have had this engine for over 25 years with minor issues, and got the engine serviced as required, seems nobody wants to service this engine anymore they all say it's too old for them...so it's time to learn myself.<br /><br />Issue: With a good battery and even when jumpered to a car battery with the car running, I get almost no cranking from the electric start (it just tugs a bit). Manual pull starting did no good as far as getting the engine going, but was easy enough to pull (nothing seized). Tried some engine start fluid ( removed spark plugs and squirted it in) and got a sputter only once. Tried and tried pull starting to no avail (would manual pull and try to get the starter to help crank with my buddy running the ignition switch full on at the same time. Jumper wires got warm , so juice was flowing. I am guessing the starter motor needs to be pulled out and checked, maybe brushes ? , maybe corrosion on wiring ? Can it be rebuilt or where can I buy a new one?<br /><br />Before I do all that, I am wondering if wire corrosion or connection issues could be the real culprit, so an easy trick for checking the starter motor directly would be a good idea. Can I run power direct to the starter for testing, with out causing damage?<br /><br />The engine was last running two seasons ago, and this issue of a poor starter cranking power was getting worse and worse before. We always thought it was because we had a bad battery in the boat. I have noticed a few topics that talk about getting all terminals and connections shiny clean, tight, and re-waterproofing...maybe I should redo the battery terminals, maybe all the wires between the battery and the engine....is this a common issue?

 

[briannh1234]

Re: Mercury 115, Vintage 1976, Starter/Ignition Trouble

vintage eh - these things are not like wine - they do not get better with age. However when you look a the price of a new engine these days ...<br /><br />When you were using the jumper cables, did you just jump from the car battery to the boat battery. If so, it still did not eliminate any potential wiring problems between the boat battery and the engine. Since checking or replacing those cables is cheaper than working on the starter I would go ahead and start there first.<br /><br />Starting fluid is considered a bad idea with these engines (and probably all two-strokes.) The reason is that the starting fluid has no oil in it to lubricate the moving parts. Use some of the premix (gas and oil mixed) in a squirt bottle instead. This should at least make the engine fart.<br /><br />If you boat battery is fully charged (get it tested at you local auto parts place that offers free testing) then bypass your cable assembly with your jumper cables. Negative from the batt to a solid ground on the engine. Positive from the batt to the side of the starter relay. I wouldn't bypass the relay.<br /><br />The most common issue with these engines is by far the carberators. If the engine was put away 2 year's ago with gas and oil mix still in the carbs, then the gas evaporated and the oil is now probably gumming things up. Once you get it cranking, if you see gas comming out the front of the carbs then the float in the carb is stuck.<br /><br />Good luck<br />- Brian

 

[Ben Konopacky]

Re: Mercury 115, Vintage 1976, Starter/Ignition Trouble

Hi Rob;just went with this myself.old wires corosion (salt)broken insulation. Start out with a ohme meter,clean the motor to cable connector first disconnect and clean all terminels.ohme all wires before hooking them back on the term. the male cable conn.has a split, open it up a little so it makes a good conniction.and check the wiring circuts from one end to the other .do it with the manual at hand.it has good schematic dwg. GOOD LUCK

 

[Clams Canino]

Re: Mercury 115, Vintage 1976, Starter/Ignition Trouble

Jump directly to the starter and see if it works.<br /><br />If not... you need a starter. <br /><br />I have 12 of them.... but I'm "closed" for a move from NH to SC and all is packed.<br /><br />-W

 

[Chris1956]

Re: Mercury 115, Vintage 1976, Starter/Ignition Trouble

Rob, I had a problem where the positive battery cable had gotten a nick in the insulation, and the salt had rotted out all but 2-3 strands of the the cable. Since it was under the insulation, it was hard to see, and since the two strands were good, the ohn meter did not pick it up. The starter just wanted to crank slow!<br />Jumping the car to the boat's battery had no effect, since the juice still had to travel the same bad cable.