how to find a hole in motor block? 1983 merc 40hp

i was told that the motor i picked up has a small hole in the block somewhere but i haven't been able to locate it from the outside, i was told that it was leaking water. i picked up this motor to use as a parts motor(electrical) for another motor and now that i have the other one working i figured i got time to see if i can get this one working. 1982 40hp sn# 6053095

maybe first step should be hook it up to water and see what happens? i guess i could've done that before writing this post but i just thought of it.

any advice for the best plan of attack for taking the motor apart and looking for the hole?
is there a common place for holes to form on these motors assuming that it didn't throw a rod?
i'm thinking 1 remove power head, 2 exhaust baffle cover, 3 cylinder cover.
i've got an experienced aluminum welder for help so not worried about that.

Any way you could put an air fitting to it, and blow low pressure air into the cooling system? That would help you without making the water mess in the garage.

Roger

excellent idea, thanks roger.

well i got the motor apart but didn't find a hole. starting to wonder if it was a gasket leak and the previous owner just thought there was a hole. the good news is the pistons and everything look to be in great shape, i'd guess this motor has fairly low hours for it's age.

i ordered a gasket kit and going to try and put it back together but am wondering what type of gasket sealant should i use? the manual says i should use permatex on the crankcase cover but there are a million options for permatex?

https://www.amazon.com/Three-Bond-Sealant-Liquid-Gasket/dp/B007TWXI1K

going to be re assembling the motor this weekend. anyone have some tips, tricks or things to watch out for?