75HP Yamaha know nothing about it

Hi I know little about outboards,mercs,and nothing about Yamahas.
I am considering buying a boat that has a 75HP yamaha on it.
It is 3cyl,compression is 6bar I'm told,no idea what that is in psi,but a little low I think,but I am going to check it on Monday.What psi should I be looking for to make it a "I'll consider it".I'll also be checking for spark as it has been laid up for three years.
I looked for the number but cannot see it,I have looked either side of the transom bracket haven't had a chance to really look under the hood yet,is there anywhere on the powerhead I may find the #.
At a guess I think it may be about '80-'85,but I'll trawl the web over the weekend to see if I can find anything that looks like it.

All advice and suggestions greatly appreciated.Thank you.

6 bar would be just a touch under 90 psi which would be a little low for this model.

Yami never published compression readings for these, but most 3 cylinder models of mid-80 vintage would have had 120-150 psi from factory.

I generally look for anything over 100 psi on a motor of this age.

Since it has been "layed up", count on replacing the water pump (kit), rebuilding the carbs, giving it new sparkplugs and gear oil. And yes, definately check for spark - you could be looking at upwards of 400 bucks worth of "stuff" before she is ready for the water, so factor that into the price (triple that if you will need a shop to do the work for you).

A running mid 80's 75 horse would normally sell for well under 1000 bucks. Given this one has been sitting, if the compression is ok and it has spark I would be hesitant to pay more than 500 or 600 bucks for it...

Thank you Graham,hoping to pick the lot,motor,boat in need of some serious TLC and trailer for about $300,well the euro equivalent. Thanks again.

That's a really good price. Even if everything turns out to be "junk" you could get your money back just selling the lower unit off the motor - good deal...

I hope so or my ever patient wife might become anything but.Picked the following #'s of the welch plug,300676,and 60881 of the carbs,all three are the same.And boy does this motor look small compared to my beautiful merc800

Should have stuck to mercs

Ok folks I'm in the doghouse 'cause I seem to have purchased a ball of ^&*(.All help going to be needed and appreciated as always.Here's what I've got. No idea what year,no numbers other than 300676 on the welsh plug,688-00 on the block,casting number,68801 on all three carbs with KEI HIN made in Japan as well.
It originated in USA I'm told,amazing how "sitting for two years" has now made it to "4 or 5 years.. Ah dum dum me.Probably closer to nine or ten
Anyway this is what I've got,105 on no's 1 and 3,90 on 2,with a very old auto gauge,will not shift into reverse,but that is a shift rod/link problem,someone has relieved me of the power t/t.
Lower unit hasn't had a change since it left the factory.But I did get the impeller changed and a good pumping tell tale and water seems to circulate all through the motor but seem to pump it out the front of the unit between the unit and leg as well as out the tell tale and exhaust??. There seem to have been some work done on the block as well as the water plate,gray green at the spark plugs is a different colour to the block, navy blue
So what am I looking for? Anyone with an inkling of an idea what age of a dinosaur am I working with and where can I get a parts break down like the crowley marine for merc parts. Apart from the fact that I really should take it and drop it in the North Atlantic I just don't like letting it go that easy. $260 is a little too much to drop over board and it does start and run very easy

I'm still plugging at this motor,unfortunately I'm a little hamfisted and had a small accident,don't ask, Can the fuel intake nozzle on the carb be replaced as I can't find a part # on the parts list that I have for this motor,I also need the air box or whatever you call it that bolts on in front of the carbs ?Any help as always is greatly appreciated.