1998 Johnson 115hp Fast Strike - Tapping Noise (Video) - Need Advice

[antimattercrusader]

Hello! I have a '98 115hp Fast Strike on a pontoon boat. A few weeks ago, I was running around 4000rpm and experienced a sudden reduction of power. I immediately brought the throttle back and the engine died. After a few minutes, I attempted to start it; it didn't start easily but it did; and with reduced power when I tried to accelerate. So, I continued on my way at a low speed/throttle for a few minutes and noticed this tapping noise.





I shut the engine down; and checked to confirm I have oil. The oil tank was full; to such an extend I wonder if the oil injection was actually putting oil in the engine. I don't really have a solid grasp of the number of hours used since I filled it, but it seems very little oil was used. One would wonder how the engine didn't have an issue earlier; but I use this boat for work and rarely run it hard. Lots of idling around and stopping every few minutes. Very rarely go above 3000rpm, so maybe it never got overheated? Or perhaps I'm just suffering from confirmation bias. In anycase, I put oil directly in the tank to get a ratio of around 50:1 and waited an hour or so to mix as much as possible. I restarted the engine and it seems to run; develop proper power. However...

• I have poor idle Performance. It will die when I attempt to switch gears.
• The tapping Noise (but less severe than in the video) still exists at low RPM. I either don't hear it or it goes away at higher RPM.
• The tapping noise doesn't happen until after the engine is warm
• I've since put probably 5 hours on it, it hasn't blown or gotten worse.

Wondering what your thoughts are? Did I screw this engine; bad bearing etc? Could it be something else?


Anyway, any input is greatly appreciated.

[antimattercrusader]

I just read the "Rule #1 before posting" - after posting, clearly. My apologies.


I am not 100% sure on the model/serial. However, I've attached photos of the engine here.

[ChampioNman]

Nothing obvious jumps out in the out of the water pictures except the missing clear sleeve over the throttle roller. Start it up on muffs and take a long screwdriver and hold it to your ear and the block all over it. You should be able to find the source of the tapping.

[antimattercrusader]

Quick update: Not sure what caused the tapping noise, but the engine has inconsistent compression (from 120 to 60) so I replaced it with something else.