please help!!! 73 mercury 20 hp problems

[jdhucks]

ok here is what i have... its a 73 mercury 20 hp it was baught new in 73 by my grand dad my dad got it when he passed and about a month ago he gave it to me.. so this thing means alot to me and i want to get it goin again it was in my dads barn for maybe 10 to 15 years... when i got it it was locked up wouldnt turn over at all got that to break loose by soaking the cylinders with wd 40... just to to see if it would run i put fuel/oil mix in the cylinders to see if it would bust off guess what 1st pull she fired right off and died after all the fuel was out the cylinders i was amazed lol but n e ways i rebuilt carb because it sat up so long i figured it wouldnt hurt trust me it deff needed it...hooked the new fuel lines up and new bulb figured id have me a beast of a motor for wat im doin with it n e way but it crank up and dies after about 5 seconds u can keep chokeing it by pullin it and pushin it and it would run for about a min try=ied tunnin the carb and i can screw it in all the way in or out and no changes..... so i got a manual to see if i could win this little battle done the spark test plugs will jump half inch gap easy with hardcore fire done a crompession check the top cylinder got 65psi the bottom 55 so ithink thats alot of my problem my theory is that its the rings still stuck in the piston itself or maybe i broke one in the process of freeing it up... my brother thinks it may be the reeds wat do you guys think??? thanks and happy new year!!

 

[bktheking]

Re: please help!!! 73 mercury 20 hp problems

Check compression using a known good tester and then report back.

 

[mr 88]

Re: please help!!! 73 mercury 20 hp problems

You have a fuel delivery problem.As bking noted double check compression. A 2 stroke with low compression is very hard to start without feeding it fuel as you did. After the initial start they are easier to fire up with that symptom.My next step would be to go to main forum and look under Engine FAQ's then Awakening a sleeping outboard. You may have a clogged fuel filter,bad diaphragm, clogged up carb,all of the above and who knows what else.I can almost guarantee you the reeds are not the problem.

 

[bktheking]

Re: please help!!! 73 mercury 20 hp problems

The reason I mention compression is that you free'd up a stuck motor, just cause it's now free doesn't mean it's healthy IE- compression.

 

[jdhucks]

Re: please help!!! 73 mercury 20 hp problems

i did do the compression check as stated in my 1 st thread number one got 65 psi number two got 55 i wonder if the rings are stuck in the poston if u understand what im sayin........ thanks guys for ur in put keep it comming

 

[jdhucks]

Re: please help!!! 73 mercury 20 hp problems

ok i read the thread as mr 88 said and the only thing i did different was used wd 40 instead of 2 cycle oil so i feel im on the right track but i dont wanna throw away money for something thats not the problem.... thanks again guys

 

[merc850]

Re: please help!!! 73 mercury 20 hp problems

I would rest the motor horizontally - carb down, remove the spark plugs, turn the crank so that both pistons are even, then spray Power Tune into both holes. let sit for awhile then repeat. Add some oil as well and leave for a day. (I have seen Amsoil synthetic restore compression on engines by as much as 30#.)

 

[bktheking]

Re: please help!!! 73 mercury 20 hp problems

Agreed, those compression numbers are not good. If you have a ring issue you need to free them up. Reeds- doubt it, they rarely give problems. I think you have a combination of carb issue as well as low compression. Try and get the numbers up and reclean the carb.

 

[jerryjerry05]

Re: please help!!! 73 mercury 20 hp problems

Got a screw in comp tester?Get one.
Hook it up and remove the other plug.Then start pulling and pulling and pulling.
When the needle stops going up then you can stop and go to the other cylinder and do it again.
If it's been setting then the carb jets could be clogged.The idle jet is on the side of the main jet and needs to be unplugged.It's a itty bitty teeny tiny hole.Look for it.
Then the fuel pump and hoses need to be rebuilt/replaced.
Ethanol is a problem on older motors and equipment.J

 

[jbjennings]

Re: please help!!! 73 mercury 20 hp problems

Agreed, those compression numbers are not good. If you have a ring issue you need to free them up. Reeds- doubt it, they rarely give problems. I think you have a combination of carb issue as well as low compression. Try and get the numbers up and reclean the carb.

Ditto from me.
I just wanted to add that you have a motor that really requires some decent amount of skill and access to the right machinist to get back in really good shape. Almost without a doubt, your lower unit has water in it because the '73 has a mild steel drive shaft instead of stainless. There are probably countless early 70s merc 200s that are hanging on a fence somewhere with a good powerhead but bad lower unit. To repair the lower unit, you need someone to put a sleeve on your driveshaft or build it up with a spray welder and cut it back down to get a good seal on the shaft in order to keep water out. Possibly for the prop shaft as well. If there's water in it now, then you're sure to have pitted bearings and gears after that length of time in the barn.
I only mention this because if it were my grandpappy's motor, I'd want to restore it, too.
My point is that you should check the lower unit for water right away, then consider how much you are willing to invest at this time to get it restored. Used powerheads for your motor are easy to find, the lower unit is the killer. You also may want to rewire it, as the wire and insulation on those get brittle over time.
Your water pump impeller is doubtless bad, and you shouldn't run it without replacing it. I'd have a powerhead with good compression before I'd invest anything in it.
What state do you live in? There may be help available.........
BTW, those motors are really awesome when in good shape, and there's lots of parts motors out there, as they sold lots of 'em. We had several of them when I was a kid, and they took a lot of abuse. They could be fun to start when cold, as well, if they weren't perfectly tuned.
Good luck with yours,
JBJ

 

[jdhucks]

Re: please help!!! 73 mercury 20 hp problems

i live in south carolina... but i did take the lower unit off to inspect everything and surprisingly it looked good but i do want to get a ss shaft one of these days.... o and jerry i do have the screw in type comp tester and the gas in it is 10% ethanol and ur right my brothers 08 50hp yammy it still runs good but to a good ear u can tell it and they are good motors i can remember it on the river with my brother and dad dont remember many things but i do that lol