Mercury 4.5 1984 1 cyl.

olliebird

Seaman Apprentice
Joined
Sep 17, 2008
Messages
49
A couple weeks ago I bought a package deal on a 12 ft. semi-v heavy alum. boat with 2 motors. One was a Johnson JW14 and the other a 1984 Mercury 4.5 single cyl. Neither motor has been run for several years. Finally got the JW14 running after replacing bad coil wire and rebuilding carb and cleaning out gas tank but now it is running HOT, anyway what this post is about is the 4.5. I haven"t started working on it yet, clean carb checking ignition and such mostly because I don"t have a gas tank but I would rather use the JW14 on my light 11ft. flat bottom as at 80 yrs. of age the Mercury is a might bit to be lifting in and out onto the boat and loading back into my pickup truck, I know, had a 1956 M/W 5hp sea king until the top piston locked up and scored piston and cyl. wall pretty bad about 4 weeks ago . Hated to see her go, had it since 1962.

Now, after all this bull%^$* I will get to my question, how good of a motor (traditionally)is the 4.5 Mercury, have they been reliable and dependable? I hate to start on it and it not be worth a lot of work getting it going. The guy said both motors were running good when his Dad put them in the barn about 10 yrs ago, well, the JW14 sure wasn't working so I don"t know what to expect on this one......
 
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emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: Mercury 4.5 1984 1 cyl.

Ollie, the single-cyl Merc has been in production in one form or another since the early-60's. They started out as a 3.9 hp and your '84 4.5 is just an upgraded version of the 3.9. It'll have electronic ignition, so spark shouldn't be too much of an issue.

I'd recommend removing the carb and cleaning it out, shouldn't require much more than a good blast of carb cleaner unless it has sat with nasty old fuel in it.

You'll want to throw a new impeller in there, they are quite small on these motors; the vanes will lose flexibility and stay curled-up instead of flexing out to the walls of the pump insert, and pumping properly.

Impellers are inexpensive and not too bad to work on. One nut on the leading edge of the L/U, and one nut from underneath the anti-ventilation plate, by the water intake screen, and it should drop down. Leave it in the gear you had it in before dropping the L/U. Most folks grease-up the flat of the driveshaft to hold the impeller key in place, and then put a tie-wrap around the impeller to cinch the blades into a tighter circle, until the impeller is dropped into the pump cartridge. Pretty basic stuff.

Drain/refill the miniscule amount of gear oil in the L/U, feed 'er good 50:1 premix and she should give good service. The little egg-beaters don't make a lot of power but will troll reliably for hours on end, sipping fuel.

Certainly worth playing with if it's decent condition, if it was a Salty Dog I'd think twice, but if it's clean there's no reason why it can't be put back in service.

HTH........ed
 
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