Mariner 9.9 vent screw

[accord_guy]

I'm having trouble with the gearcase vent screw <br />on a 91 9.9 mariner. It's a smaller hole tucked right under the cavitation plate. When I try to get a replacement screw they want to sell me a conventional large head screw similar to the drain plug only minus the magnet. They say that's what the computer says is the correct part. The guy before me had an allen head bolt in there but it leaked and I had water in the lower unit. Any ideas would be greatly appreciated.

 

[mjbrueck]

Re: Mariner 9.9 vent screw

It sounds like they're trying to sell you the right part. I haven't seen your engine, but on every engine I've owned the drain and vent screws are similar.

 

[accord_guy]

Re: Mariner 9.9 vent screw

I wish that were true. This vent is no more <br />than 1/4 inch screw.

 

[rodbolt]

Re: Mariner 9.9 vent screw

some of the older mercs had a diffent vent than drain. they were smaller but desined the same. still were a flat headed screw with a gasket underneath. maybe your unit is older than you think. but an allen headed bolt with no gasket will leak. if the allen heded bolt has a head and the correct thread size try making a gasket for it. an oring wont work,dont even try it.