90 psi Mercury 175 XRi?

[JBMac]

I'm looking to buy this motor from an individual for my Valero. The engine is clean as a whistle, the owner is looking to put a four stroke on his
boat for better mileage. Here's the problem: when I went to look at it, it starts right up and runs great. After warming up, I used my brand new fancy Harbor Freight compression tester. The engine read 90lbs (+- 2-3 psi) across all 6 cylinders. I'm not sure I trust the tester- I may try to plumb it to my shop compressor and see how it compares to the compressors guage. If it truly is 90 psi- and the cylinders are in good shape, is it likely that a hone and ring job would give me years of service?

[Euroski]

I wouldn't trust that HF tester! See if U can borrow real one from a mechanic.

[johnboy 88 vegas]

If the cylinders are that close to even on compression then the motor is probably just fine even though the real comp number is way off. Very few motors die with comp numbers staying that close together but stranger things have happened. Like Euroski said....get another gauge.

[JBMac]

I went ahead and bought it- $1800, I felt that was a good deal. It came with a 5 blade prop, I can't find any markings on it, it will definitely have to go to a prop shop for clean up. Its in pretty good shape, but it looks like it's hit a sandbar or two, maybe from loading on the trailer at the ramp, pretty scuffed up. I'm hoping this might be a good "ski" prop for the Valero, or at least some trade value. I plan to do some basic mods to the engine (cut tuner, solid mounts, Bobs nose cone, shave heads.)
I went ahead and pulled the starboard head to check cylinder condition- still has nice cross-hatching, piston topsides look good.

In my research on this site, I've seen a lot of recommendations to use a machine shop that specializes in outboards. Any recommendations for a shop in FL? The local NAPA shop has done me right on several past jobs of tractor / skid steer engines- wondering if shaving the heads on this motor would be fine to have them do?Thanks in advance for the help.

[johnboy 88 vegas]

Shaving heads means better fuel...don't forget the 93 octane

[coffeeguy]

It may have bleed down ports in the cylinders plus a faulty gauge would give low readings. I think with bleed down ports a stock one is about 115psi.

[home made tunnel]

What you have is a BUYERs compression guage. It shows lower than real numbers ! I have one of those HF gauges, and use it to knock the price down when I buy stuff haha.

[ProComp]

Any good machine shop can cut heads.
On stock fishing motor heads Ive gone 60 thou and run 91 octane. Never had an issue.

Buyers compression guage......lol

[CVX20SPRINT]

Had a guy come to look at my sled I had for sale and he brought his buyers gauge.After he used his I pulled out two that I had and redid the compression test.Both of mine were with-in a lb. or so and a lot higher than his.Don't think he was expecting me to pull out a gauge.

[johnboy 88 vegas]

A set of late model 2 liter heads with thin head gaskets puts you on the edge with pump gas....mine was about 155 lbs.