I need to pick someones brain for some answers.

I bought this old boat or traded for it a couple of weeks ago and waiting on the guy to get me papers on it. The motor is a 1977 70 Johnson, seems to run great in the tub. I took it to the lake today to give it a test and see what else it needed while waiting. It started and idled on the first crank with choke but when I put it in gear , forward or reverse, it died. I started it again no problem and idled then putting in gear it died, this repeated several times. I set the cold idle up to get more high idle. After about 5 minutes on high idle I got it into gear and it putted around pretty good with no hits or misses. And when hit full throttle at stand still it set the rear in the water with force, (its on a 15 foot trihull). I was happy with the way it ran and performed but it wont slow idle with out dieing and if been shut off for a few minutes it dies when in gear.
Now my questions is : what is the low RPM suppose to be set at?
What is the cold idle high idle should be at ?
I don't have a manual yet but one is in the mail . I have searched over the forums and don't seem to find a question related to my concerns. Is this engine just normally slow to warm up? Or , do I have other problems to look for as fuel filter , carbs needing cleaned or ??. It was running or said it was fine from previous owner and I have no reason to doubt his word yet. It has fresh fuel , all hoses bulbs etc seem to be in good shape and the bulb holds firm after setting a few minutes with no leak back. Can someone give me some areas to check out ?

Re: I need to pick someones brain for some answers.

As has been said so many times, have you checked the compression? My guess is that you have a non-firing cylinder or a weak cylinder. Rule out a dead horse (weak cylinder) first with the compression test. If that passes, move on to checking for spark, dirty carburetor (s), link & sync, etc.

Better wait for that manual, or put up with us guys' guesses.

Re: I need to pick someones brain for some answers.

I took the fuel filter off and discovered that from a previous owner/mechanic the fuel filter gasket was bad so they used black silicone on both sides of the gasket and it was covering the screen, cleaned that out and made a new gasket. Took the breather housing off and discovered another bad gasket, made another one there. Took the housing from the carbs and discovered another bad gasket there and made new gaskets all the way around. All hoses were soft and pliable and no cracks. Put everything back together and pulled the spark plugs, the looked new and gapped them at .030. Compression was #1 100. #2 105 #3 100. Jumped a spark 5/8 inch strong and blue. So put everything back together and going to the lake to try it again in a couple of days.