1993 Yamaha 9.9 repair

[n6rfm]

Hi Gang,

In the proccess of repairing my 9.9.

http://webpages.charter.net/n6rfm/winter_2008_2009.htm

After installing a new head gasket, I torqued down the head bolts to spec in order as described in the shop manual. The six bolts under the valve cover were fine (these are bigger). Sadly, the two bolts which are external on the head and adjacent to the cooling passages, continued to turn and did not get to the desired tightness, but only to about half the target. I suspect that corrosion over the years has diminished the threads in the head. The bolts get pretty tight, but not as specified in the manual.

My question is: Since the external bolts are much smaller than the internal head bolts, are the external ones torqued to the same extent? The manual indicates 22 ft*lbs and does not make any distinction. I suspect I have to install some helicoils to address this anyway.

Thanks for the advice in advance,

Bob

 

[sdsaw]

Re: 1993 Yamaha 9.9 repair

Bob,
Very interesting blog on your project you have going there. Wish I had documented mine when I had it apart.

On the head bolts, the 8mm bolts get torqued to 11ft pounds on the first round and 22ft lbs on the second.
The smaller 6mm bolts get 2.2lbs followed with 5.8lbs on the second round... I think you twisted the smaller bolts right off!
You may want to get two new 6mm bolts because you may have compromised the strength of the one that didn't break off

I rebuilt my '88 9.9 because I was getting water and exhaust soot in my motor oil. Turned out finding that I had a corroded oil tank where the exhaust tube runs down through the center of it and plenty of clogged cooling passages.
It's amazing how many people(including myself) have issues with these Yamahas in regards to cooling passages clogging up... saltwater is brutal on these motors

Have you ever noticed any black soot in your oil?
Oil filter ever plug up?

Get back to me if you have any questions on that motor... I've been through a lot with mine since '96

Hope this helps and good luck with it.
Scott

 

[rodbolt]

Re: 1993 Yamaha 9.9 repair

the distinction between the 8mm and 6mm bolts is clearly printed and pictured in the YAMAHA service manual, dunno about the aftermarket toilet paper ones.
but now you need to remove the head,trash the gasket as its already been crushed.
inspect for thread damage and repair as nessasary.
now your a tad older and much wiser and know a 6mm bolt cant take 22 ft lbs .

 

[n6rfm]

Re: 1993 Yamaha 9.9 repair

Thanks Scott and Rodbolt,

LOL. Yup, definitely older, hopefully wiser. Amazing what can now be found in the General Specifications section of the repair manual!

Scott -No overt signs of soot or water in crankcase oil, nor plugging of filter. I just checked. There were a very few small pieces of grit which might be carbon on the filter. We'll see if that holds true when back up and running.

Will fire off an update when done.

Bob

 

[n6rfm]

1993 Yamaha 9.9 repair - update

1993 Yamaha 9.9 repair - update

Hi Gang,

Finally got the motor re-assembled, cooling circuit working properly after the angioplasty and running! Yeah. Thanks for the gentle advice along the way. In the end, I had a mechanic take a look as it was hard to start and ran rough. Turns out I missed some crud plugging the enrichment circuit. My bad. BTW, thanks RodBolt for explaining how the needle valve in that circuit works. Cool (or should I say hot wax)!

I had adjusted the valve clearance to the middle of the spec range but the mechanic also re-set these just out of the wider end. Now the motor has a distinctive purr. Perhaps this does not matter, but just curious if this makes sense?

Thanks,

Bob