What should the compression be? I hooked the tester up yesterday and got 60 psi. That seems a bit low to me…
Somebody told us Wall Street fell but we were so poor we couldn’t tell. Cotton was short and the weeds were tall but Mr. Obama gonna save us all
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From what I can find, it looks like 130-140 psi is normal. Did you use a srew in type guage, or a push in? That’s on a new, or fresh powerhead, but certainly 60 psi is not good. the numbers on all cylinders should be within 10% of each other.
…Politicians aren’t the “Oldest Profession”, but the results are still the same!!!
Did you open the throttle wide open when checking?
Most folks don’t know to do that, but it is how to
check boat motor compression. Think about it, you need to
be pulling in the optimum air into the motor.
Rick
What year motor? Should be at least 100 psi. It will run on 60 psi (if it is fairly even on both cylinders) but might be tough idling with foot submerged and of course lower power. Try a light decarb, and try using the motor…that might bring compression #'s up some. I just went through a compression fiasco on my Rude so am telling you from recent experience
Mike
12’ Jon boat twin 300 Verados
quote:Now I have a question? If you're checking compression, and compression is so weak on a two stroke motor, that the butterfly in the carb. becomes a variable, then aren't we being consumed by the details? In other words, if the motor doesn't have enough compression to over ride the butterfly, isn't there another problem? I don't think you can starve a two stroke for air enough to affect the compression test. But, I've been wrong before, and I'm sure I will be again! Seeya, Scott
Originally posted by ECU1984Did you open the throttle wide open when checking?
Most folks don’t know to do that, but it is how to
check boat motor compression. Think about it, you need to
be pulling in the optimum air into the motor.Rick
…Politicians aren’t the “Oldest Profession”, but the results are still the same!!!
I was just always told that by my father who was a NASCAR engine builder for 30 years. I later read it in a factory outboard service manual also. I would like to hear Chris V’s opinion on it.
Rick
Googgled a few service manuals and each one states to open choke and throttle.
Disable ignition system and ground spark plug wires to engine block.
If wires are not labeled, make sure you label plug wires before disconnecting, (use white masking tape to write TOP, MIDDLE, BOTTOM or 1,2,3, etc) You would hate to not know what order to reconnect them wires. Some engines have wires marked or distributor has spark numbers, check and make sure.
Next, remove ALL spark plugs and keep them in order so that they can be replaced into their original sockets in the same order.
Place the compression hose into spark hole #1 and zero the guage.
Check your choke and make sure it is in the open position. Make sure the throttle is open all the way. If your system is equipped with a neutral safety switch, you may need to manually engage the throttle from the engine block while the remote is in neutral. You want to allow as much air to enter the bore as possible to get an accurate reading and a neutral safety switch will prevent the battery from turning the engine unless it is in neutral. Be careful, flywheel and starter will move so ensure your hand is not in the way of any moving parts.
Crank the engine and observe the reading. Each cylinder should be cranked an equal number of times and / or seconds in order to get an accurate reading for comparison. If you have pull to start, pull it 4-5 times for each cylinder as long as you do the same for each cylinder. Make sure you zero out the dial each time.
2 strokes doesnt matter
4 strokes yes, you have to open the throttle
quote:No problem here Buddy, like you, I was only looking for the right way?
Originally posted by ECU1984Googgled a few service manuals and each one states to open choke and throttle.
Disable ignition system and ground spark plug wires to engine block.
If wires are not labeled, make sure you label plug wires before disconnecting, (use white masking tape to write TOP, MIDDLE, BOTTOM or 1,2,3, etc) You would hate to not know what order to reconnect them wires. Some engines have wires marked or distributor has spark numbers, check and make sure.
Next, remove ALL spark plugs and keep them in order so that they can be replaced into their original sockets in the same order.
Place the compression hose into spark hole #1 and zero the guage.
Check your choke and make sure it is in the open position. Make sure the throttle is open all the way. If your system is equipped with a neutral safety switch, you may need to manually engage the throttle from the engine block while the remote is in neutral. You want to allow as much air to enter the bore as possible to get an accurate reading and a neutral safety switch will prevent the battery from turning the engine unless it is in neutral. Be careful, flywheel and starter will move so ensure your hand is not in the way of any moving parts.
Crank the engine and observe the reading. Each cylinder should be cranked an equal number of times and / or seconds in order to get an accurate reading for comparison. If you have pull to start, pull it 4-5 times for each cylinder as long as you do the same for each cylinder. Make sure you zero out the dial each time.
…Politicians aren’t the “Oldest Profession”, but the results are still the same!!!
It’s all good! I learned something too. I have seen over 10lb jump by opening throttle. I also was taught to do it on a warm engine and not cold also. I quess the rings and cylinders expand when hot…just quessing. I always refer to Chris V, seems to be a very sharp outboard man.
Rick
C.V.(Team Charleston Marine) seems to be the very best around these parts!
…Politicians aren’t the “Oldest Profession”, but the results are still the same!!!
I changed the head gasket and plugs and got it up to 100 psi and fire off and run tonight. I’m going to run some decarb through it and then drop it in the water to run it for a while.
Next step is to take it back apart and put the charging kit on there so my battery will recharge when it runs!
Somebody told us Wall Street fell but we were so poor we couldn’t tell. Cotton was short and the weeds were tall but Mr. Obama gonna save us all
xHCFKx
Good Luck!
…Politicians aren’t the “Oldest Profession”, but the results are still the same!!!
on a 4 stroke outboard, it can make close to 100#s difference in compression number