I recently purchased a 1988 Cobalt with a 5.7 Mercruiser with around 500 hrs. on it. What would you suggest I do to eliminate problems
I dont know the service history of your boat ( maybe you dont either) but here goes....
Check out yourself--or have a tech check out--the engine's ignition and electrical system from the key switch to the alternator and starter. Water + electricity = long term problems.
The sterndrive has bellows, which seal the drive and exhaust and shift from water entry into the boat. These need to be changed at least every three years, more frequently if you keep the boat in the water, especially saltwater. ( Barnacles can rip the bellows). If a bellows fails, your boat will sink. Many boaters change them annually and I cant argue with them. Here's a link for how to handle that:
Is it freshwater cooled ( closed cooling ) or raw water cooled? In any case the risers and manifolds usually need to be replaced ( or removed and cleaned out--a dirty, time consuming job) every 5 -7 years since scale builds up and clogs the works.
Remove the gearcase and have it pressure tested to test the propshaft seals. These seals keep water out of the gearcase. They are robust, but should be checked bi-annually.
Properly winterize the boat ( even its in long-term storage in a warm climate): here's another link for ya:
I could go on, but you should buy a service manual like those published by Clymer from an outfit like Doug Russel Marine: www.dougrussel.com
Search our maintenance section here on the website, like us on Facebook as we are always doling out tips, and make friends with some other boaters to share experience with.
Good Luck! Cobalt is a great boat!
I hope you also had a compression test done,you can also check the condition of the plugs (they can tell the story as well) also you can do a seal test on the lower unit as well as checking the lube in the drive (colour,smell,feel) will tell you a lot of what has been done and what has not, engine oil as well, colour, smell,feel , routine maintenance is one of the best things that can be done for a marine unit but all to often they get ignored because most people just go down to the marina jump on the boat and go, and if something does go wrong most will say "I will fix it later" and then they forget about it. I just sold my 99 2655 bayliner and was so confident in it I told the people who bought it that I would fix anything on it for a year ,Never heard from them except a card at Christmas saying that it's been the best thing they bought and had a great year on it.