Re: 1991 200hp Johnson
I've got a 1990 200 hp and it works great.
I'm not an expert, but might be able to get you started. The most basic things to look for/check:
First verify the year. It is part of the Model number you should be able to find somewhere on the transom bracket. It's in code, so you'll either have to find a guide to Johnson model numbers, or post the model number here. It should start with J200 or something like that. There should be EI (which indicates "90") at the end, or within a digit or two of the end of the model number.
You should specifically ask him if everything on the engine is original or if it's been rebuilt or major parts changed such as the powerhead, leg, etc. Sometimes rebuilt or remanufactured engines are really fine, but sometimes they're a conglomerate of parts that makes future service a nightmare. (BTDT, both types!) NOTE: if you can't easily find the model number on the transom bracket or if he can't show it to you, you're "rebuilt" suspicions should be alerted because sometimes remanufactured engines have the tag removed because they are no longer accurate as to model number and features.
You really should check the compression on all 6 cylinders or have someone check it for you. That engine won't have really high compression - normal is 90-95 or so, all within 10%.
You should check the lower unit oil - drain it and look at it to see if there's any signs of water or metal in there. A little sign of water is not a deal killer because you can replace gaskets to tighten it up, but you should know and make the deal contingent on being able to solve that problem. You should also specifically ask the seller when he last changed it and if he's ever seen any signs of water intrusion like cloudy/milky oil, since he could have recently changed it and therefore the nice oil you see might not be typical.
what condition is the prop in? Is it aluminum or stainless steel? If you're not sure, ask him. Props can be changed, but (a) it's an indication on how it's been used and (b) a stainless steel prop is actually pretty valuable and a good thing to see!
You should run it for at least 10 minutes or so on the water. How does it start? Idle? go smoothly at "no wake" speed?, accelerate? cruise smoothly? Go wide open smoothly? and what are the wide open throttle RPMs? The factory specified WOT RPM's for my 1990 is something like 5500-5800, I'd imagine the '91 should be the same. Anything less than that, you'd want to know why.
Is the charging system working well - it should show 13.5+ volts (even 14 or so) when the engine is running.
Ask when the water pump was last serviced. Watch the "tell tale" stream and/or water pressure gauge if he has one. The stream should be strong. Again, an iffy water pump is not a deal killer because chances are you'll service it right away just to make sure it's solid (cheap, easy, necessary maintenance).
Check the status of the "VRO" (AKA "OMS") fuel+ oil pump. Is it still intact? When was it last updated or changed? If it's still intact, look at the entire system from the oil tank, the lines on up to the fuel pump - just to see how the lines look, any leakage, etc.
Of course, look at the general condition of the motor, including under the cowling. Does it look well cared for or like it's been neglected? How do the fuel lines, etc. look?
That will get you started.
Good luck.
