Low compression

[mtodd1402]

I bought a 2001 246 with an 8.2gsi (502ci) last fall, engine has about 475 hours on the clock. Only got to use it for a week last year before it got too cold but it ran strong and was a blast.

Had my local marina winterize it and wrap it.

As spring came around we unwrapped it and did some basic maintenance
Oil change/Filter
Water separator
Drive oil
Impeller
Cap, Rotor, wires and plugs
Replaced a leaking oil cooler.

Took it to the lake for Memorial Day, launched it and it ran fine at idle but back-fired under load.

My mechanic believed the back firing was caused by bad injectors.
We replaced all 8 injectors and launched the boat last weekend. It had a hard time starting and had no power.

Pulled it back out and ran it on muffs, it hesitates to start without giving it some throttle. If we increase the throttle it will either not rev and cut out or hesitate for many seconds before revving-up.

My mechanic did a compression test today:
1 115 psi (port front)
2 90 psi (starboard front)
3 90 psi
4 100 psi
5 80 psi
6 90 psi
7 80 psi (port rear)
8 105psi (starboard rear)

He doesn’t seem to have a clear guess as to what is causing the loss of power so I was hoping maybe someone here has seen something similar and has a solution.

The summer is quickly passing us by and we have a total of zero hours on the lake. Would love to get a few days in before it is back to hibernation.

Thanks, y’all!

[bruceb58]

That's pretty low compression.

Was the engine warm?
Was the throttle plate wide open?
personally, I would buy a quality compression tester and repeat the test myself.