Re: thermostat cover on 9.9 johnson
As an update, I had problems with removing the latch completely as the latch bolt couldnt be removed with the thermostat cover and head getting in the way. I got the head off and the thermostat cover and took a look. Yep thermostat quite cruddy and a neoprene seal or bit of rubber lodged in there too. Out with the old, in with a new thermostat and seal.
Again the problem was going to be tool clearance for the bottom head bolts when getting them back on. I can't find any tool that would really do this... maybe one of those through socket wrenches, but that might even be tight. I have found a solution to tighten the bottom two bolts, and adding it here for future reference.
I took a 1/2" socket that has a 1/4"hex shaft, i.e. a socket designed to be chucked in a drill. I reduced the hex shaft length so it would fit inside the outboard lower cover but still have the shaft project out enough past the plane of the thermo cover so I could attach a 1/4" spanner. I purchased a high quality Sidchrome 1/4" ring spanner, making sure it fit the hex shaft of the socket bit firmly... this is key to be able to apply enought torque to the bolt head. You dont want a loose fit on the hex shaft or else it will just slip, or a poor quality ring spanner will just strip... Anyway use the ring spanner on the sockets hex shaft to tighten up the bolts. Works really well!
For those not familiar, there is not enough room around the head of the bolt for a ring spanner to be attached directly to the bolt, or the head of any 1/2"spanner for that matter.
Anyway hope that helps any future readers who have a similar problem.