Motor problems…

Today scooting across the lake all of a sudden motor started knocking lost power and now continues knocking. Sounds like a rod is out. Any other thoughts???

Wear in the bearings eigther between the rod and crankshaft or between the piston and piston pin. Probably between the rod and crankshaft. What make of motor and is it a lower piston?

My guess is you lost a piston, too. Not going to be cheap!

Mercury 115 inline 6 cylinder

Now you got me worried, mine is the same motor. Only thing is mine only now fires on 5 instead of 6 cylinders. It seems to fire on all 6 when at WOT. It really stammers at an idle. The 4th one down has no spark getting to it. I’ve changed the coils and wires around and replaced the square ignition pack thingy too. Still nothing to that 4th one. The odd thing is it does run the same speed it did before and seems fine wide open. Just thought I’d mention all of this if anyone knows the answer as long as were on the subject of a 115 hp inline 6 motor. I read on the net something about a bad stator could make it do this.

Thanks,
Ron

Take it in to a respectable shop………

Also, I wouldn’t recommend running a motor with a dead cylinder. Things are going to get “hot” and unspent fuel is going to cause problems.

Having a bad running car motor is “bearable” due to average RPMS are only around 2000.

However, when you are cranking 4000, 5000, or even 6000 rpms out of any motor that is not performing the way it should, things are going to wreak havoc. That dead cylinder is “dead weight”. It is not “banging”, therefore throwing off the harmonics of the motor at that high of rpms. That can cause great abuse on a motor.

Also, be aware of detonation in your boat motors. When the manufacture calls for 91 or 93 octane gas………RUN THAT GAS!!!!!!!! If you do not, you will create premature detonation. So, instead of the gas igniting on the down swing of the piston, it ignites at TDC (top dead center). What this does is “hammers” the bearing. Bearings do just fine on “normal” rotation. However, if you take a 7lb sledge hammer and smack that piston while the rod is straight up/down on the crank bearing, it is going to put a “dent” in the bearing. Eventually, that “dent” is going to create a “knock” because there is now a gap.

Basic rules for running a 2 stroke:
1) Run the proper octane gas.
2) Do NOT use generic oil.
3) Let the motor warm up before hitting WOT or even half throttle. Warming up a motor doesn’t mean to let it run for 30 seconds. It means to bring the motor to normal operating temperature BEFORE hitting the throttle to rpms above 2000.
4) Change your spark plugs EVERY SPRING. Spark plugs will wear out with age, not just usage. Weak spark not only gives you poor performance, but it will lead to the problems listed above. They are cheap, replace them every year.
5) Keep your fuel filters/carbs/injectors clean. Run the proper solvents/cleaners through them. When gas gets lean, it burns out the pistons, shortening engine life.
6) Lastly, do free rev your motor in neutral. ESPECIALLY when we are talking a cold motor with NO lubrication anywhere. NEVER free rev your motor, it is a QUICK way to knock out a bearing.

Run your boat motor the way you would your auto. You let your car warm up when it is cold and you don’t “floor” your car gas pedal when you start your car. Those are the two biggest factors I see people doing on the water.

Hey Gary, thanks for all the help. My next choice was taking it in somewhere to have it looked at. I was just hoping somebody had a really simple solution that I hadn’t tried. I never get lucky enough to have it just be simple though.

Thanks again for the great information,
Ron

Unless you have a “service manual” and the proper electrical testing tools with wiring schematics………I would just be forced into stating to suck it up and take it to a shop………Sorry to sound cold…..But when it comes to electrical, it is very tough for the average “garage mechanic” to even track and fix without experience of the motor……..Good luck!

Well BAD news…
Went down to the boat today with tools in hand, started out pulling spark plugs hoping maybe one was just fouled up, to my surprise there was one fouled up number 4, it was fouled up with melted metal shavings. So the next little toy I whip out of my box of goodies is a compression tester. After cranking her over and running back to look at the gauge there was nothing. Checked the others and they were all well over a hundred and all about the same give or take 5 psi. So yep I do believe I BLEW her up! On a good note found a replacement motor for her and will be picking it up after my trip to Milacs tomorrow for some fishing with my brother. So on the dark view of it lost a good motor had to pay out probably less then it would have cost to rebuild this one GOOD note, but still going fishing!

Dont just scrap the old motor. I had an old Johnson 70 that I blew up. I tore it apart and sold the pieces for more than I would have gotten for a running motor.

Thats Good news on finding another motor so soon gjk, i’ve got a friend thats got a 90 evie thats going to cost $2500 to rebuild, the marina said they knew a guy looking for parts for that same motor so he’s going to part it out and make more on it than he paid for it.

Thanks for the advice….
Well it is now 2:50 a.m. and time to get ready to hit the road for some fishing on Milacs hoping to catch some of those eye’s everyone up there keep saying are jumping in the boats…