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I have a marine Yamaha outboard t50tlra what should the

Hello I have a marine...
Hello I have a marine Yamaha outboard t50tlra what should the compression be cold on this unit
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Answered in 3 minutes by:
3/23/2018
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16,753
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Hi Jim, Jason here. When the engine was new, it would have had compression readings in the 190 to 210 PSI range. As the engine wears and tears that number will go down. The specification in regards ***** ***** minimum compression reading on this engine is 122 PSI. Anything below that and the engine would be considered worn out, damaged, or possibly needed a valve adjustment.

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Customer reply replied 29 days ago
What should the stater output be?
Customer reply replied 29 days ago
I have compression readings in the 60’s for cylinders 1,2, and 4 number 3 at 35

When you say stator output, are you talking about the ignition side of the stator or the battery charging side of the stator?

Those compression readings are no good. You can either do a leakdown test on the engine next, and see where that lost compression is leaking off to. Or, just pull the head and see if the valves are any good or see if the pistons and or cylinder walls are damaged.

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Customer reply replied 29 days ago
Ignition side of the stator, I’m currently working on this model of engine I’m going to check the valves for the compression issues, but also have no spark

Are you using a DVA to check the voltage?

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Customer reply replied 29 days ago
Have not yet tested but I do have a DVA

G​ot it. At cranking RPM, the stator output should be roughly 140VDC, give or take 10%

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16,753
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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