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Johnson 225 Knocking sound

J

Jadtob

New member
Hello Everyone.
thanks for always sharing your knowledge.. I have a problem with my Scarab 302. My port motor 1995 Johnson 225 started knocking while in gear. It is a constant noise that goes away while in neutral. This startted happening while running on the water. I came back home parked the boat and left it alone. today I drained lu oil. It was milky and I did not see any metal pieces. I filled her up with gear oil ran it in the hose and knowcking is gone. Any Ideas on what this may be? Im afraid if I take her out on the water again noise will cme back it can actually be too late creating more damage.
thanks for your help.

Im tryin to upload video of when noise was happening but not sure how to do it on the forum.
 
Hi and welcome. Has it ever hit a rock? How much end play on the prop shaft? Prop shaft bent? How much up/ down play on prop shaft?
 
Last edited:
timguy said:
Hi and welcome. Has it ever hit a rock? How much end play on the prop shaft? Prop shaft bent? How much up/ down play on prop shaft?[/QUOTE

Tim: Since Ive had the boat I havet hit a rock. Ive only owned it for about a month now. The prop is intact However that LU skeg is chipped in the bottom which leads me to think that at some
Point it did hit something.
There is minor play on the prop compared to other unit. Im going to remove the prop to inspect the up/down play. Shaft is straight.
Im trying to figure out if I should just replace the entire LU or if maybe just a part or two. Which could save me good amount of money.
Click to expand...
 
Replace what is needed only, they are so darned expensive. Not hard to work on. I'm doing a 150 right now, severe rock strike. Badly bent shaft. The guy "backed" into a rock. Ouch!
 
Is this actually a "knock"... like a connecting rod knock, or more-so a "tap" like a wrist pin or chipped gear tooth?

Is the noise constant, like every revolution of the crankshaft etc... OR... of an undetermined period of time. If the latter, is there any jerking of the engine involved... and also since the noise is present while in gear, is the noise present at "all" rpms?
 
I checked the compression about a month ago and it was good. I would have to check again to rule this out but I dont think the noise is on the power head.
 
joereeves said:
Is this actually a "knock"... like a connecting rod knock, or more-so a "tap" like a wrist pin or chipped gear tooth?

Is the noise constant, like every revolution of the crankshaft etc... OR... of an undetermined period of time. If the latter, is there any jerking of the engine involved... and also since the noise is present while in gear, is the noise present at "all" rpms?
Click to expand...

I want to say it is more like a tap. Like a chipped tooth. I noticed while running Iddle. It tried going faster but noise would increase with rpms. I also tried while in neutral and nothing was heard even with higher rpms. The motor would shake every time the nocking sound was heard.
 
Jadtob said:
I want to say it is more like a tap. Like a chipped tooth. I noticed while running Iddle. It tried going faster but noise would increase with rpms. I also tried while in neutral and nothing was heard even with higher rpms. The motor would shake every time the nocking sound was heard.
Click to expand...

You've said nothing about the engine jerking, like it was hitting a submerged object at the higher rpm (in gear only)... but in reality would be jumping out of and back into gear, so I hesitate to bring that possibility up... but the thought is there.

It truly sound more like a chipped gear tooth problem.

However, apparently, the gearcase needs to be dismantled, in which case both of the above will become obvious if they exists.
 
More questions pal, you got the real pro's helping you on this one (excluding me). When did it start the noise? Did it come on little by little? Does it make the noise in reverse? Water was mixed into the gearcase for some reason. Lesson learned. Check for water in gearcase before purchase. I forgot to remind someone else of that on a recent post, dah!
 
Pappy, I have replaced ring gears and pinions where a chip will not be heard unless power up or slow down. Really evident in automotive applications. Its beyond me, however, how the gear could have gotten chipped in the case featured here. So your idea may be the most likely probability, especially with water entering the housing.
 
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