Knocking in mid section

[bkfish]

1993 175 Fastrike #VJ175GLETR
I've got a loud knocking sound coming from what sounds like upper midsection
while idling in nuetral.With motor off,in gear,I can twist prop forwards,backwards and pretty much duplicate the "knock". Never done this before but seems like alot of movement twisting prop.Turned motor over by hand with plugs removed and all pistons stroking but did not try to put any resistance on them. Is there some test I can do to determine in what direction I need to go? Powerhead,lower unit?
Always appreciate the help,Thanks

[Scotty B]

Drain your lower unit oil and see how it looks....
You may have something coming apart and the noise could be traveling up the drive shaft making you think its coming from mid section

I lost a rear end in my truck once and swore the tranny was bad. When I held the shifter you could feel it but it was just traveling up drive shaft to tranny
kinda luck a string and a can hahaha

Good luck let us know what you find

[bkfish]

Yea,I would definetly rather repair lower unit than powerhead$. Guess I can drop the lower and hook a hose to the flushing port,bust it off, and see how it sounds.
Have A Good One

[rudetech1]

Sounds like a chipped tooth on the pinion gear! You have caught it before catostophic failure ! Should be some metal in the gear lube on this one.

[bkfish]

I must say I'm quit relieved it's probably my lower unit based on your response.
I'll start tearing into this weekend and post back what I find.Might help someboby else down the road. Sure is nice to be able to come over here to BBC
and get some good,solid, "free" advice you can turn a wrench on.
Thanks

[bkfish]

Ok,Drained oil this morning with maybe a thimble full of water ahead of oil.
Top magnet clean,bottom magnet with slight graphite looking powder.Oil looks
relatively clean with slight gray swirl.Taking lower unit off now.If I start motor hooked to flushing port without lower,is this a reliable test to determine to determine if my problem is powerhead or lowerunit?
Thanks

[bkfish]

Just started it up without lowerunit.......It has the death rattle,lower part of powerhead.What's the next step?Based on the age of this motor,it probably would'nt make a lot of sense to just repair possibly the one cyl.or crank bearing right? Especially with the labor involved.

[ChampioNman]

Compression test time.

[bkfish]

Just did comp.test
#1@95 all else right at 90.
Heeeelp

[Tom G.]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by bkfish &raquo;</td></tr><tr><td class="quote">Just did comp.test
#1@95 all else right at 90.
Heeeelp</td></tr></table>

Me? I'd either bore scope or pull the heads and see with my own 2 eyes what the cylinders look like... No 2 comp. gauges are the same, so I would do this for my peace of mind.

I think I'd also look into tearing it down enough to see the crank and related components. If you catch it now, it more than likely will be cheaper than after it goes.

[bkfish]

Appreciate your input but I think,for me anyway,I need to consider having this one rebuilt or a re-manufactured powerhead$$$ouch.I'm pretty decent with a wrench be this would definetly be un charted water.No warranty on my work.
Thanks

[ChampioNman]

Find a well known OMC wrench in your area.

[Tom G.]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by bkfish &raquo;</td></tr><tr><td class="quote">Appreciate your input but I think,for me anyway,I need to consider having this one rebuilt or a re-manufactured powerhead$$$ouch.I'm pretty decent with a wrench be this would definetly be un charted water.No warranty on my work.
Thanks</td></tr></table>

Get in touch with Rudetech1 here - he's in the Houston area, and he's the man on the OMC's. He posted above in the thread - shoot him an IM for info.

[TexasHawkeye]

I would recommend Rudetech1 also. He is honest and knows his stuff.

[bkfish]

Thanks for the help.