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Need help to start 1984 4.5hp

M

Migillicuty

New member
New to the forum. I just got a1984 mercury 4.5hp. I changed the broken water pump impeller and made sure it has spark using a spark tester. Tried starting it with a drill and the carb is just leaking on the bottom. Im unsure how to remove this carb off with the choke assembly right in the way. I'm hesitant to hit this thing in fear of not being able to get replacement gaskets. Any advice what to do from here?
 
The choke assembly must be removed in order to remove the starboard nut on the carb. Precautionary note; once you get this engine running, do not use the stop switch to shut the engine off unless the lowerunit is submerged deeply in a bucket for adequate back pressure to shut the engine off quickly. This engine uses the 2nd generation Phasemaker ignition that can be damaged if using a flush attachment which allows the engine to run at a higher idle speed and take longer to shut off. It is best to use the choke to shut this engine off. This is a very expensive ignition system to service.
 
That's great advice thank you for that. It looks like the choke assembly is held together with one nut is that correct? The engine did actually start up and I was happy about that. I found that the lower unit shift shaft is stuck in drive. I gently tried to use pliars to twist the shaft with the lower gear unit off and it won't move. The carburator leaks pretty bad on the bottom.
 
fitz73222 said:
What do you want to work on first? The carb or the gearcase?
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The gear case. I managed to get the carb off. I took pics along the way getting that choke assembly figured out. I looked inside at the reeds and was pleased to not see any rust and they appear to be in tact.
 
fitz73222 said:
Did the engine shift before you removed the gearcase? What is the condition of the gearoil?
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I didn't bother shifting it before removing the bottom. First thing I ever did to it was inspect the impeller and found it in pieces and replaced that. Then put the bottom back on, checked for spark, put in new spark plug, then changed the gear oil. The old stuff was dark. Then started it up with fresh gas and 50:1 oil.
 
So when you attempt to shift into neutral, it wont budge? Is so, you need to drop the lower unit again and re-phase the shift shafts to the correct orientation, it happens. You should be able to rotate the shift shaft counterclockwise to get back into neutral, do not force, it should just click back, you're just overcoming spring tension. Do not by any means shift this engine into reverse without rotating the propeller or the engine running or you risk damaging the shift cam and opening up that can of worms.
 
Well either run it forward gear all the time or you're going to have to open up the lower unit and find out why it won't shift. To start you're going to have to purchase or borrow the spanner nut wrench to remove the left hand thread cover nut to gain access to the inside of the gearcase. Once the nut is removed, you simply grab the prop shaft in a vice and tap the gearcase with a deadblow hammer to expose the bearing carrier, shims, reverse gear and propshaft assembly pulled out and look for a damaged shift cam or some other reason why the shift shaft won't turn. Was there any water in this case when you drained it or just dirty gearoil?
 
One additional question, can you shift the engine with the shift lever with lower unit removed? The goal is to isolate an upper shift shaft issue from the lower shift shaft (gearcase issue)
 
So another update. I was able to play with the shift shaft and vice grips. I could spin the crank shaft by hand clock wise and see it turn the propeller. I was able to slightly twist the shift shaft enough to where it was in neautral and the propeller would no longer spin while turning the crank. However no matter what i tried it would not go into reverse. It was almost spring loaded back into drive once I et off of my twisting action. So its like the dog clutch wants to be stuck in drive. Not sure what's causing this.
 
My gut tells me that someone may have tried to shift this engine into reverse without it running or spinning the prop and now the shift cam no longer has enough throw to get it to go into reverse, it's either broken or twisted out of phase on the lower shift shaft. Needs to come apart for inspection.
 
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