1972 Mercury 4.5

[Steevano]

Ive been offered a 1972 Mercury 4.5 for $50. The boat was on a trailer and was rear ended by a car. The lower unit was damaged by the impact. The motor was bought new by guy selling it and maintained immaculately. Is it worth finding a lower unit? Finding a non running 4.5.? Or is it interchangeable with other small 2 strokes? Or should I keep looking?

 

[fitz73222]

I would make sure the engine runs before going on a lower unit hunt.. Reason being is that engine had a unique ignition system known as Phasemaker. It was Mercury's early attempt at capacitor discharge ignition while still using points that actually fired when the points were closed as opposed to a conventional magneto that fired when the points were opened. Parts are very hard to find and very expensive if you can find them. Honestly, no one works on these engines anymore so you have to educate yourself about how they work. Any lower unit from 1972-1985 4, 4.5, 7.5 and 9.8 will bolt up. Focus on anything built after 1976 since Mercury switched from problematic carbon steel driveshafts to stainless steel shafts to thwart corrosion in the seal area which would allow water to enter the gearcase through corrosion pits. If I was considering buying the motor, I would do a spark check, if it has fire (like white hot blue hear it pop) fire then remove the damaged lower unit and rig up an adapter to fit the small copper water pipe to a garden hose, turn on the water hose , put some fuel in it and see if it lights off. I have 5 of these engines from 1967-1985 so I have some experience with them. For $50 what do you have lose? My sage advice is if it doesn't have fire, walk away or if it's really clean you can sell the individual parts for way more than $50 on ebay or what have you....

 

[racerone]

Exhaust housing may be bent as well.------

 

[fitz73222]

I would make sure the engine runs before going on a lower unit hunt.. Reason being is that engine had a unique ignition system known as Phasemaker. It was Mercury's early attempt at capacitor discharge ignition while still using points that actually fired when the points were closed as opposed to a conventional magneto that fired when the points were opened. Parts are very hard to find and very expensive if you can find them. Honestly, no one works on these engines anymore so you have to educate yourself about how they work. Any lower unit from 1972-1985 4, 4.5, 7.5 and 9.8 will bolt up. Focus on anything built after 1976 since Mercury switched from problematic carbon steel driveshafts to stainless steel shafts to thwart corrosion in the seal area which would allow water to enter the gearcase through corrosion pits. If I was considering buying the motor, I would do a spark check, if it has fire (like white hot blue hear it pop) fire then remove the damaged lower unit and rig up an adapter to fit the small copper water pipe to a garden hose, turn on the water hose , put some fuel in it and see if it lights off. I have 5 of these engines from 1967-1985 so I have some experience with them. For $50 what do you have lose? My sage advice is if it doesn't have fire, walk away or if it's really clean you can sell the individual parts for way more than $50 on ebay or what have you....

Do you have pictures of the damage? Racer makes a good point....