Rattling and no power over 4mph

[Parker]

I have a 115. It idles fine but over 4mph it rattles really bad. I have checked the fuel lines and they seem fine. One lower spark plug doesn't seem to be firing and it gives off sparks and shocks when I remove the cap while it's running. All the others do not. I have put a new plug in and the same thing occurs. Any suggestions?

[tripleb]

Hey Parker,

Two words: Compression Check

[Ken]

Parker,
Could you be a little more descriptive on the symptoms? What do you mean by "rattles" - misses?
shakes? won't go over 4mph?
Can you rev it up above idle out of gear?
What year and model 115? carbed or fuel injection?
Ken K

[Parker]

Once I move the throttle forward, past 4mph, the whole engine body, shakes violently, whether it is in gear or not. I don't know how else to describe except that it seems as if it will break a motor mount or something if I continue. As far as the spark goes; I ran the motor and with some rubber handled plyers I took off each cap to the spark plugs to see if I could hear a change in the motor. Only in one plug did I not hear a change and it is the only one that gave me a shock and when I went to turn off the engine it gave off some sparks. That's the best I can describe it. Here are all the numbers from the engine. S115TLRW 6E5 L 403773 V
Thanks Ken.

[Ken]

Ok, Parker, you have a 1998 carbed Yamaha 115.
From what you are saying, it sounds like that little V-4 is hitting on only one cylinder, and maybe just barely on the other three also.
You may have major problems - hopefully not.
You need to first do what tripleb suggested - run a compression test to see if any of the cylinders are bad - broken/stuck rings or blown head gasket.
Then you need to do tests on the ignition system - could be bad coils in the stator, bad spark plug wires/coils, or a bad CDI.
If you get passed the above tests ok, then I would take a look at the fuel system. Could be clogged carbs.
All of the above can be tested as outlined in the Yamaha shop manual. If you are going to do this yourself, you're gonna need one, and some special tools.
You may want to consider having a qualified marine mechanic tackle this one for you.
Good luck [img]smile.gif[/img] ,
Ken K

[Parker]

I will run all those tests, just waiting till this storm eases up and will pull the boat. Don't have much of an option for a real mechanic to look at it, seeing as I live in the middle of nowhere on an island. I am the only option I've got! I have a service manual and most likely all the tools I will need. Thanks for all your help so far.

[Ken]

Parker,
Well, keep us informed after each test procedure. Each of the forum members will contribute what we can. No guarantees. Just honest opinions and goodwill [img]smile.gif[/img] .
Ken K

[Parker]

Thanks a lot, I will keep you informed, still have a storm here. One other thing, the battery was hooked up incorrectly (a positive on a neg) when first started up. It wasn't on long but could that have shortened something out? Just a thought.