Logo

Restarting a secondhand Mercruiser 485

markline800

New member
"Hi, I have acquired two 485s

"Hi, I have acquired two 485s (With sterndrives and all gauges etc.) that were sitting in a garage for a couple of years and need help on the procedure to restart them after such a long time. They were running fine with good compression when taken out apparently but I do not believe they were "winterized". Can I start them out of the boat without the sterndrives attached? If so what do I need to do to ensure water/exhaust flow. I have already had the transom and stringers done to accommodate these engines. Hope someone can help."
 
"Len:

It can be done. Some


"Len:

It can be done. Some of the resident 485 owners should chime in on this one. The first thing I would do is pull the spark plugs and give the cylinders a good shot of PB Blaster or some other penetrating oil and let them sit for an hour. Then I would try to turn over the engine by hand w/a B/bar and socket.

If they are not locked I would give them a tablespoon or two of engine oil and repeat the hand turn. Install new spark plugs and check/replace/set the points. Change the oil (use 30 wt.) and install a quality oil filter (not Fram).

Connect a strong battery and ground the coil output wire. Crank the engine for 20 seconds and wait for 2 mins. for the starter to cool. Repeat two or three times so that engine oil is pumped into all the engine bearings. Remove the spark plugs and perform compression tests; record the readings. What is important is the numbers should be close to each other; example: 120, 122, 125, 124.

Now pull the carbs and rebuild them. They should be soaked in carb solution for 1-2 days to loosen the hardened varnish in the idle circuits; then rinse and blow dry w/compressed air and reassemble them using new kits w/floats. Use carb specs from a manual and not the kits. Use the correct base gaskets and install.

While the carbs soak, drain the antifreeze from the blocks and heat exchangers and flush them w/clean water. Pull the end caps off the exchangers and inspect the tubes for crud; clean if needed. Replace the thermostats and pressure caps on the exchangers. Install the endcaps and fill the cooling systems w/a 50:50 mix of auto antifreeze. If you mix your own blend; use distilled water.

Connect a garden hose to the water inlet w/an adapter and use full pressure. Give the carb a shot of STARTING FLUID, INSTALL THE FLAME ARRESTOR and give it a crank. Let it warm up 5 min. as it idles at 800-900 RPMs; DON'T EXCEED 1,000 RPM's. Check for coolant and oil leaks on the engine. Change the engines' oil and filter again while the oil is hot."
 
Guy is right on as usual! Your

Guy is right on as usual! Your two biggest problems will be possible corrosion inside the engine cylinders and Shelac from old gas inside the carbs. And when you get these engines running again I would suggest chucking your old points/condensors and getting Pertronix Electronic ignitor systems. They run about $75-$90 each but well worth it in the long run.
 
"Thanks guys. I'll give th

"Thanks guys. I'll give that a go and let you know how it turns out. I have already acquired 4" exchangers (One new and the other very good) to replace the 3". I am also seriously thinking about converting over to alternators and electronic ignition. I believe the only other weakness I need to look out for are the camseals which have a tendency to leak. One of the challenges I am yet to get over is replacing the exhaust elbows (Which are 2 piece - part numbers 91025T & 91023A2). You can't find them here in Oz for love nor money and of course all the suppliers worldwide state "This part is no longer available". I got hold of some 1982 470 one piece items (Part # 72082A2 MCM) which fit fine at the transom and connect to the same bellows (70981A3). Anyone know if this is a direct replacement? Many thanks, Len"
 
"Thanks Guy, I have looked at

"Thanks Guy, I have looked at these three and the only one showing the correct exhaust elbows are perfprotech but they stats NLA - hence my looking to use the one piece 470 elbows. Thanks Len"
 
"Those are all important issue

"Those are all important issues of the MCM470 but I think I would wait until you have the engines up and running and dependable before dumping money and time imto other things. But you seem like you've done your research, that's a great start."
 
Back
Top