Will I have problems with clearances, torque settings etc. when the weather gets warmer if I reassemble parts of my engine in the current cold weather (the boat is outside and unprotected - the engine is v cold!)?
Where else do you do it !!
Well, I would not rebuild out in the open air because of the risk of airborne particles ending up in side the engine .
Also gasket sealants wont be as easy to spread if it's to cold .
It's not like working on aircraft where all the gauges are tested and kept in specific conditions .
Many times I've had to work out side with no ill effects ,on cylinder head gaskets and so on .
Commonsense and the no option clause come into it though .
assuming you arent going to do it when its -20c or something you shouldnt have any problems later with clearances.
and as far as gasket goo is concerned , thats something I do my damnedest to avoid using, dry if its in the water sytem usually , or just a thin smear of engine oil on the gasket faces elswhere..thats standard aircraft engineering practice!
You will have no problems at all, 2 tips though, a thin smear of grease under the head of all the bolts with critical torques (main ends, cyl. head etc.), and keep any gasket jointing compound in the warm (inside the house) until you want to use it (though as is mentioned, use this stuff sparingly). Do this and you will have no problems, but do not over-compensate by making the clearances tight or the torques tighter, this could cause trouble in use.
As long as you're not rebuilding the engine when it's freezing, temperature doesn't matter. You will have to retighten the cilinderhead's bolts and to readjust the valve clearances anyway after a 20 hours running . Then your engine will be perfectly tuned and will run smoother.
Don't forget to change oil and filter the same moment.