Are there any problems with testing compression with the engine tilted up. I thought I would do it with the boat in the water. Easier to get to the cylinders this way.
Compression Test With Engine Tilted Up?
- Thread starter Greyduk
- Start date
probably not. You are really looking for variances not so much absolute readings.
That said, I am always hesitant working on a motor in the water. Sometimes tilting up makes it less likely that something dropped dropped will go overboard.
If there is a risk to dropping something I tie off a small tarp under the rear of the boat and motor to catch fallen items. If you are in a private slip, adding the tarp is easier than when tied off on one side only
That said, I am always hesitant working on a motor in the water. Sometimes tilting up makes it less likely that something dropped dropped will go overboard.
If there is a risk to dropping something I tie off a small tarp under the rear of the boat and motor to catch fallen items. If you are in a private slip, adding the tarp is easier than when tied off on one side only
wrxhoon
Well-Known Member
No problem at all on two strokes. Warm engine, WOT and good battery will give you more accurate readings.
Seasick gave you an idea just in case you drop anything.
Seasick gave you an idea just in case you drop anything.
One additional thing to pay attention to is to try to crank the motor the same number of rotations for each test.
Whether or not the throttle has to be fully open or not is up for debate but with the motor on the boat , it is simple to just move the throttle all the way up.(use the shift override button so that the prop doesn't spin during the cranking.)
Whether or not the throttle has to be fully open or not is up for debate but with the motor on the boat , it is simple to just move the throttle all the way up.(use the shift override button so that the prop doesn't spin during the cranking.)
BTW-- If the controls are wired properly, the engine will NOT crank unless the prop (shifter) is dis-engaged
Just to follow up, I checked compression yesterday with the engine tilted up. It worked perfectly. Did it with the kill switch clip removed and the throttle advanced all the way in the fast idle mode. The engine is a 2000 OX66 200. All readings were within 3 PSI of each other. Thanks for the responses.
That sounds great but if I remember correctly, the compression on the two lower cylinders will be lower than the other cylinders. Their compression ratio is lower. I know for sure that is true for the SX150. I am not sure about the 200.
I don't know about that, but readings for all cylinders were 119,118,or 117 PSI.
Last edited:
I was pleased with those numbers. I don't know how you could expect any better from a 20 year old engine.
