Mercury 100 9.8 question

[Brandonhurst91]

Hopefully it's ok to post here about this... If not let me know....

But I bought a 1966 mercury 100 9.8 today. I don't know a whole lot about outboards so maybe someone can help me. I got this motor for a steal so it wasn't a huge gamble. It doesn't run right now, but the guy said he got caught up in heavy moss and the prop stopped spinning. If you pull the rope while holding the prop it will not spin. Any help on that would be appreciated. And also when I took the hood off the plugs were missing. Why would a guy take both plugs out? And does anyone know what plugs this takes? And last but not least what fuel ratio does this take?, and what fuel/ oil should I run?
I hope I didn't post in the wrong forum, or ask too many questions.

[MrPaulAR]

May wanly to take a look at boats.net as they have papers diagrams for most motors. They will be a huge help when putting it back together or looking for part numbers.

[Blackhawk19]

I can't help you with any answers but I would suggest you post this in the Mechanics Corner section on here and I'm sure someone there will help you. Just scroll down the main page and you will see it. I almost forgot, welcome to Crappie.com.

[mjm76]

I've got a 1978 model of Mercury 9.8.....If you can get it running it will probably serve you well. X2 about the diagrams on boats.net. The downside of old motors is that parts can be expensive and hard to find.

[CrappiePappy]

Hopefully it's ok to post here about this... If not let me know....

But I bought a 1966 mercury 100 9.8 today. I don't know a whole lot about outboards so maybe someone can help me. I got this motor for a steal so it wasn't a huge gamble. It doesn't run right now, but the guy said he got caught up in heavy moss and the prop stopped spinning. If you pull the rope while holding the prop it will not spin. Any help on that would be appreciated. And also when I took the hood off the plugs were missing. Why would a guy take both plugs out? And does anyone know what plugs this takes? And last but not least what fuel ratio does this take?, and what fuel/ oil should I run?
I hope I didn't post in the wrong forum, or ask too many questions.

Welcome to Crappie.com, Brandon !!

Now ... I'm just guessing here, but it sounds like this motor may have done one of a couple of things, due to getting bogged down in heavy moss.

If it has a shear pin ... that may have been sheared off, and may just need to be replaced.
It could have spun the prop or sheared the gears/teeth on the prop spindle or in the shaft linkage.
In either case ... taking the prop off & opening the lower unit would tell the tale. You might want to check the water pump impeller, too, while the lower unit case is off ... & replace it.

I have no idea why anyone would pull the sparkplugs & leave them out, as that would only create a situation where moisture could get into the piston cylinders. Check this for possible sparkplug compatability with your motor : Mercury Outboard Quicksilver Parts at The Outboard Shop home of the Mercury Outboard (and as I understand it, "perma-gap" plugs are less prone to fouling)
You might want to get some fogging oil & spray into the cylinders, let it sit for about an hour, & turn the flywheel one turn every 10-15mins ... to get the rings freed & reset. It will make starting the engine a bit harder, once you get to that point, and it will smoke a bit as it burns off the excess fogging oil.

I couldn't find an exact answer to your oil mix ratio ... so you might want to contact Mercury, or a reputable local dealer, and ask them. I'm thinking it's 50:1, but being a mid 60's motor, it could be 100:1
Another thing to consider -- E10 gasoline !! Your seals & lines may not be ethanol resistant. It may also be necessary to change the oil mix ratio ... so I'd include those things in my conversation with the Merc people.

Posting here is fine ... but, if you want, I can move this whole thread to the Mechanics Corner Forum ... or send a copy of it (where it would appear in BOTH forums).
Ain't no such thing as "too many questions" ... you're not only getting your questions answered, but others are benefitting from the information/discussion, as well. That's part of what the site is all about ... teaching/learning !!

... cp

[Barnacle Bill]

The prop probably has a spun hub. A prop shop can make it like new. Plugs are NGK BR6S or Champion equivalent gapped to .025. Gas mixture is 50:1.