Re: 1988 Mercury?
They made a 70HP 3cyl and a 75HP 4cyl in 1988<br />If you can get the serial number off the transom bracket, that will help clarify for sure.<br /><br />Before purchase it is always a good idea to check the compression in each cylinder. They should be equal to each other, and preferably less than 10 psi difference.<br /><br />Check the lower unit oil, for consistency and signs of metallic particles on the drain plug. Check for milky color, which would be a sign of leaky seals.<br /><br />Lower gearcase oil should be changed, and new water pump assembly (or at least the impeller). You need to see a steady water stream out the tell-tale to ensure adequate cooling. Don't run it dry, and don't rev it up on muffs.<br /><br />Hopefully the motor was winterized with some form of fogging oil prior to storage. Inspect the plugs, and replace them if questionable.<br /><br />Carb rebuild is a good idea. Quite likely it is varnished over time. Better safe than sorry.<br /><br />Check power tilt & trim function, if equipped.<br /><br />You may want to run oil mix in the gas tank until you can verify that the oil injection system is functioning properly. Mark a line on the oil storage reservoir, and make sure it is being consumed at the proper rate.<br /><br />Use only new gas, not the old gas that has been in storage for 5 years if the tank is included.<br /><br />I can't comment on specific reliability of the motor, but can say that my motor of that vintage which is a 40HP 4cyl runs great.<br /><br />If you don't end up purchasing that motor, shoot me an email with specifics. I'd love to have 70 ponies on the back of my boat!<br /><br />Best of luck.
