Any tech conventions when marking cylinders during compression testing?

[swade]

Bit of detective work here.

I have a curiosity that had bugged me about my 99 bf130 since i bought it and the boat used. I *know* this motor is an affected serial number for the block casting.
I know zero about the history of the motor.

The motor also had white pen markings next to each plug on the valve cover, 145, 150,145, then a yellow mark. no number. (like a tech was writing compression numbers are something, just white , yellow ink).

here's the thing...those numbers are not right as the manual states 199-228 & 300 psi. Now when I test compression it is dead on, i mean dead on 215, 215, 215, 215 maybe could be a variance of 5lbs due to my
my gauge but i tested it also against my air compressor and it's not more than 5lbs off through the range. The boat hour gauge had 275 hours but you know those don't mean anything. So obviously these numbers are excellent.

No markings under the hood of if the block replacement had been done.

Just curious what a tech may think, like if there's a convention. The readings are so good and the numbers odd ALONG with the yellow mark on the bottom one (#4 iirc) it almost makes me wonder if a powerhead could have been done in the past and the original valve cover put back on. But this just may be wishful thinking =) but i'm not worried about the motor runs. great. Just curious what you guys make of that

 

[jgmo]

Ya got me wondering now too. Could be that the yellow "mark" was to indicate the valve lash had been adjusted or checked. Or, it could be how many times Sally the receptionist has turned him down for a date. I like your "the powerhead has been replaced" scenario.

But, at the risk of sounding completely clueless, what's really got me stumped is the 300 psi. What is that?

 

[swade]

hi jgmo,

lol@ the sally theory

i meant 199-228psi at 300rpm =) that's the compression specs in the manual iirc

yeah i'm stumped myself. 145,150,145, yellow mark #4 *right* by the plugs, no idea what those would signify. Here's the thing too, grease pen marks too...i mean can't be from the home owner doing a wonky test themselves, had to come from a tech.

When i bought it couple years ago i said oh look the last compression test (i didn't know specs at that point). THen i saw the yellow mark and said oh no, that cylinder is surely very low/shot i bet. So I tested at 210 dead on to factory specs, and i've been stumped ever since.

I just tested the compression again as i was doing oil,etc regular yearly maintenance and it just got me thinking again.

 

[jgmo]

Well, she turned me down 5 times, so it wasn't very funny to me.......JUST KIDDING! I mean, who could turn down a homely mug like mine .

You are probably closer to the truth than you think. I was serious when I said the marks could be for valve adjustment. That is something I and others do to keep track as we move along a tune up. I've even seen guys use little scribe marks. You have to do something when you are "multi-tasking in a busy shop and the phone is ringing and the boss is yelling. It's just that if you're working on a customer's engine, you should be wiping it all off when you're done and NOT be putting scratches in the finish!

The important thing is, no matter WHAT it was that they were up to, it sounds like they left the thing in pretty doggone good shape! I mean, WOW! 215 compression on a used outboard! Starts and runs great!? I should be so lucky!

Sounds like you got a pretty good deal and a nice boat. The mystery of the markings will, in this case, have to go down as a "bonus" feature. Something to ponder while keeping your mind off the slow fishing.

Cheers!

 

[swade]

Hi Jgmo, lol really appreciate the input. Yeah it's probably 205-210 thereabouts which is still in spec, but surprisingly damn good in my book. I always figured my old gauge was really off so I just always looked for consistency.

until this time I rigged it up to my air compressor to compare 3 gauges at once to see how far off the comp gauge could be. Course can only get to 120 (so could get less accurate at 200) but it's always within 5lbs of the other gauges so i imagine that carries through the range.

Well let it stay as mystery. if it aint broke...