Hi, I have read a previous thread from 2005 with a similar scenario to mine. That thread appeared to finish with a low cylinder compression.
Here is my problem.
I have a merc 4.5 ser #711xxxx that i just got hold of with intention of fixing up. I have not been able to get this motor running. The previous owner suggested that it hasn't been run in a while.
Checked so far:
1. Spark - good 3/8"+ when holding spark plug away from block - it will jump this gap, when i turn the flywheel manually. Not every single time, but most times - if i vary the dist between 1/4" to 1/2"- vast majority make a spark
2. Fuel - after checking everything else i made the assumptin that the fuel pump was done. I tried pumping it but nothign was going through - so i replaced it. Now i assume that there may not have been anything wrong. The new one seems to be working. To test this - i removed the hose from the carb intake and dangled it downward and put the cover back on - so that i could pull the cord. a squeeze on the primer bulb would gush the fuel through, and pulling the cord would send just a little trickle through with each pull. I guessed this is ok. Neither pump would push fuel out with the hose pointing upwards (why i assumed the original pump was done)
3. I opened the top of the carb intake and checked the float and needle - while i didn't clean it i made a few measurements and it all looked ok as per the manual. I put it back with new gaskets. I didn't remove the carb from the head yet.
4. I poked a compression tester through the flap on the hood and attached it in place of the spark plug (single cylinder). Put the hood back on and pulled 5-6 times. The needle went up to around 110 - i'll have to try it again to be sure. but then it bled down to 90 psi over the space of about 5mins. Does it matter if it can keep the pressure? or is it just how much pressure it can create? This was with the engine cold - i'm not sure if the throttle was open or closed.
The only time the engine has run was after all this, i made a slight adjustment to the idle screw on the carb. I screwed it fully in, then backed it out 2 full turns. It ran once, for less than 10seconds, then wouldn't start again. I played with it adjusting in/out for a while but still no luck - i pull it sounds like it might be firing once, but doesn't start.
When i pull it i hear a little squeek as it stops rotating -is this normal - sounds like rubber maybe?
Also - shoud i be expected to turn the driveshaft easiy by hand? (I removed the lower unit) I can turn it but i have to grip it firmly and turn. It won't spin by freely itself - i'm wondering this, in case it is putting extra load on the engine - however i can pull the cord freely and it isn't hard to pull.
Many thanks in advance for any suggestions/advice.
Here is my problem.
I have a merc 4.5 ser #711xxxx that i just got hold of with intention of fixing up. I have not been able to get this motor running. The previous owner suggested that it hasn't been run in a while.
Checked so far:
1. Spark - good 3/8"+ when holding spark plug away from block - it will jump this gap, when i turn the flywheel manually. Not every single time, but most times - if i vary the dist between 1/4" to 1/2"- vast majority make a spark
2. Fuel - after checking everything else i made the assumptin that the fuel pump was done. I tried pumping it but nothign was going through - so i replaced it. Now i assume that there may not have been anything wrong. The new one seems to be working. To test this - i removed the hose from the carb intake and dangled it downward and put the cover back on - so that i could pull the cord. a squeeze on the primer bulb would gush the fuel through, and pulling the cord would send just a little trickle through with each pull. I guessed this is ok. Neither pump would push fuel out with the hose pointing upwards (why i assumed the original pump was done)
3. I opened the top of the carb intake and checked the float and needle - while i didn't clean it i made a few measurements and it all looked ok as per the manual. I put it back with new gaskets. I didn't remove the carb from the head yet.
4. I poked a compression tester through the flap on the hood and attached it in place of the spark plug (single cylinder). Put the hood back on and pulled 5-6 times. The needle went up to around 110 - i'll have to try it again to be sure. but then it bled down to 90 psi over the space of about 5mins. Does it matter if it can keep the pressure? or is it just how much pressure it can create? This was with the engine cold - i'm not sure if the throttle was open or closed.
The only time the engine has run was after all this, i made a slight adjustment to the idle screw on the carb. I screwed it fully in, then backed it out 2 full turns. It ran once, for less than 10seconds, then wouldn't start again. I played with it adjusting in/out for a while but still no luck - i pull it sounds like it might be firing once, but doesn't start.
When i pull it i hear a little squeek as it stops rotating -is this normal - sounds like rubber maybe?
Also - shoud i be expected to turn the driveshaft easiy by hand? (I removed the lower unit) I can turn it but i have to grip it firmly and turn. It won't spin by freely itself - i'm wondering this, in case it is putting extra load on the engine - however i can pull the cord freely and it isn't hard to pull.
Many thanks in advance for any suggestions/advice.