Old Motor with Low Hours but looks new

[twister123]

Just purchased a used 1985 185 VRO motor that looks new, but compression is only 80 psi each. The seller said the motor sat for 5yr. I poured some 2 stroke oil into each cylinder fired it up for about 10 min and took the compression. Is this the best way to take a compression reading for an old motor? Will it make a difference if I run the motor longer?

[Raceman]

If you've only got 80 lbs there's one of the following:

1. internal problem with engine
2. defective guage
3. low battery voltage, or bad starter/starter circuit (slow cranking speed)
4. incorrect technique

If it's technique related, I'd recommend you pull all sparkplugs, make sure the battery is hot, open the throttle (this only makes a very slight difference on most engines) and make sure the compression hits the guage for at least 3 revolutions.

The last one I checked for somebody that had low compression accross the board (lower than yours actually) had been run without oil. Looking in the cyls with a bore scope revealed severe scuffing.

I've never seen sitting for several years lower compression. A lot of my stuff sits forever. My old dual engine stacker boat had been in storage since the 70's when I bought it without being cranked and the compression was normal. The guy did NOTHING to store it, (no fogging, etc) except stickin' it in the barn.

[neveredge]

Norris don't you know that "stickin it in the barn" is the absolute best way to preserve something?

Why just look at all those old Corvettes and Yenko Camaros that have been found under an old cover in a barn without any damage whatsoever...


80 lbs on a 185 crossflow may be correct. That motor had the softer heads on it. It was basically the earlier 200 just re-rated when the HP rating method was changed. Stick a bore light in there and see if there is any damage.

The 185s don't have a lot of bottom end to them. I believe the port hieghts are the same as the 235 small bore.

[76baja18ft]

80 probably isnt way out of line on it.. was the compression the same on all cylinders?

[Raceman]

Ouch............... I read right past the 185 VRO and it didn't register in my tired ole' brain as an OMC. I don't ever give OMC advice because I don't know ANYTHING about em (as my post above clearly displays). I was thinkin' 80 lbs in a Merc.

Sorry guys............ I'll go back to sleep now.

[Raceman]

Here's another excuse: I'm not supposed to be out of bed at 6.36 AM anyhow:confused:. Any opinions voiced after 1 AM and before 10 AM are void.;)

[delawarerick]

80 if even is ok remember omc had the service bulletin and the thick head gasket was suggested for longitivity. Rick

[twister123]

Thanks guys but I never heard of an engine with such low compression rating. All the manuals suggest 100 psi or higher. At least they were all measured at 80 psi.