Topic: 9.9/15HP T-stat gasket PN? Not on M.E. – Antique Outboard Motor Club,Inc

This topic has 19 replies, 9 voices, and was last updated 6 years ago by fleetwin.

Viewing 10 posts - 1 through 10 (of 20 total)

1 2 →

Author

Posts
March 22, 2018 at 10:10 pm #9473
johnyrude200
Participant
Here is a picture of the 3 different t-stat cover gaskets for the various generations of the 9.9/15hp motors. I have an issue here. The first production run models from 74-76, I can’t find anywhere the part number for these gaskets. They are specific to these motors. I luckily have had 3-4 from a buyout I did a couple of years back but now am all out.

My OEM parts books (as-in the 1974 parts books I have in hard copy) list the cover gasket as 318917, but that is INCORRECT. M.E. also references this number. This number refers the the middle gasket, not the original one on the left.

Note the far left gasket is what I’m after. The middle one somewhat fits but really is the wrong gasket. I know this because I keep getting motors for M.Y. 74-76 in here that have this gasket installed, with all sorts of instant gasket gooped on them or no gasket at all, leaking all over the place because people don’t realize the suppliers are giving us the wrong ones.
March 22, 2018 at 10:16 pm #72877
Mumbles
Participant
You have to use your model number to get the correct gasket for these motors. I learned that the hard way wasting time running back and forth to my dealer.
March 22, 2018 at 10:40 pm #72878
johnyrude200
Participant
There are no dealers supplying this stuff, or even care to, that I know of around here.

Just looking for an online supplier rather than making them myself! Not sure what better place to look than the original parts books which I own, but there has to be a part number for these floating around.
March 22, 2018 at 11:11 pm #72879
retiredoz
Participant
US Member
My ’75 Johnson parts book refers to 318917, but the sketch looks like the one on the right in your picture. The one in the middle appears to be 329920, (originally 321387), used in later models (I looked at ’85).
March 22, 2018 at 11:44 pm #72882
johnyrude200
Participant
Yeah, if anyone can identify the left most gasket PN, that would be helpful.

I mean what is everyone doing to replace these on their 74-76 models? Id like to know if someone has a source for them. Cutting gasket material gets old fast with things like this and as we all know the t-stat cover is a PIA to remove on these motors due to the cowel latch.
March 22, 2018 at 11:49 pm #72883
retiredoz
Participant
US Member
Are you saying the one the book calls for doesn’t work ?
March 23, 2018 at 12:04 am #72884
outbdnut2
Participant
US Member
I know we don’t like to use aftermarket parts, but I thought I’d take a look and see what Sierra shows. Interesting that my 2004 Sierra catalog says the one on the left is 18-2905, replacing OMC 329920 (which may be the correct OMC number), but when I look online, what’s available now is an 18-2905-9 and looks like the middle gasket in your photo, and the 18-2905 without the -9 does not come up anymore. I guess they think the -9 should fit them both, which is probably wrong.

From the photos, it looks like the middle one can have that lower right hole trimmed off and it then would look like the one on the left, but there must be other differences since you are finding it doesn’t fit – but you already knew that.

The one on the right in your photo is Sierra 18-0397, or OMC 0318917 – both available at marineengine.com
Dave
March 23, 2018 at 12:11 am #72885
Mumbles
Participant
The one on the right is the one included in the 386699 powerhead gasket set for the ’74 to ’76 9.9/15 horse motors.

Attachments:
March 23, 2018 at 3:58 am #72895
johnyrude200
Participant
retiredoz, yes, the book recommended gaskets are wrong. Just got off the phone with Dan in TN and he reminded me of this conversation from a few years back.

Apprently the gasket Im looking for was all but discontinued back in the 70’s because all of the ‘74-76 motors had been recommended for a cylinder head change from the 8 to 9 hole t-stat cover.

The funny thing is I get these ‘74-76 motors in all original configuration showing up each year by customers or cleanouts I do. The dilemma for me is were talking about a 44 year old motor and pulling the original cylinder head, especially if its been moused out or salted, isnt always a good option. So pulling the t-stat cover and replacing the gasket is the better option.

I mean, it’s not like head gaskets give up very often when a motor isnt overheated of course.

So Dan recommended just having the gaskets made by an outside company. Makes sense.

Outboardnut – the newer style gaskets really dont fit right. They “kinda” fit but not without a generous helping of instant gasket seal, and Ive seen plenty of these original motors show up with cob-job seals which we now know why.

I guess I was lucky at one of my buyouts to find a stash of these. They must have been sitting in the drawer of the closed marina for 40 years. You wouldnt believe some of the things I see thrown out in these situations.
March 23, 2018 at 4:24 am #72896
rmhxruss
Participant
318917 fits all 74, 75 units and some 76 depending on the suffix letter. 321387 329920 the rest.
Author

Posts