175hp cylinder walls and absurd compression results

racerone

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Facts-------It takes time to develop a technique to use telescopic gauges !-----I believe you are not there yet.--------Note---I used to work in a shop where measuring to + / - dimensions of 20 millionth of an inch was done.-----When I was hired for my last full time job I was handed a training exercise requiring measurements with telescopic gauges.----I handed it back to the instructor.----He said " that did not take you very long " -----Then he came out and said that my measurement were 100% correct !!
 

pastorbud

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Facts-------It takes time to develop a technique to use telescopic gauges !-----I believe you are not there yet.--------Note---I used to work in a shop where measuring to + / - dimensions of 20 millionth of an inch was done.-----When I was hired for my last full time job I was handed a training exercise requiring measurements with telescopic gauges.----I handed it back to the instructor.----He said " that did not take you very long " -----Then he came out and said that my measurement were 100% correct !!

They don’t make them like that anymore I’m afraid. My two auto mechanic guys have never done this measurement. My Small engine mechanic has, but he was not available today.

I saw one video where the student angled the handle down so that it bottomed out and centered on the rim of the cylinder. I tried that but it didn’t feel right.
 

pastorbud

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I wish I could afford a dial gauge, but those things ain’t cheap. Can’t find a loaner.
 

flyingscott

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Take a piston ring and put it in the hole. Now push it down about an inch. When you open the telescoping gauge you want the ends to rest on the ring. This will insure the gauge is straight in the hole. Take 2 measurements there. Push it down farther and repeat. Make sure the ring gap does not line up with the ports.
 

pastorbud

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Take a piston ring and put it in the hole. Now push it down about an inch. When you open the telescoping gauge you want the ends to rest on the ring. This will insure the gauge is straight in the hole. Take 2 measurements there. Push it down farther and repeat. Make sure the ring gap does not line up with the ports.

Hey, cool trick! I don’t have a piston ring but it’s given me some ideas.

Wonder if I could snag one from an automotive junkyard?
 
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pastorbud

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I tried a different trick for getting the gauge squared up.

I cut a piece of 1/4 inch ID brake line and put it in a flaring tool to hold it square. Then I put the gauge handle through the tube.

With the flaring tool laying on top of the cylinder and lined up diagonally with the head bolt holes, I had the telescoping gauge squared up and centered.

But the measurements still came in at 3.97 and 3.98.

I brought my digital caliper down to NAPA and compared its readings with the one at the shop. My caliper is measuring the same as theirs.
 

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racerone

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They build these engines in a modern factory.----The standard bore is 3.500.----Thus your measurements are FLAWED and it takes time to learn the technique of using telescopic gauges.
 

pastorbud

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Next I’m gonna try setting the telescoping gauge to 3.50 and locking it before inserting it, just to see what that feels like in the cylinder.

That may give some idea what a proper alignment feels like.
 

pastorbud

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I have found some dial gauges for $60 or so on Amazon. Lord knows if they’re any good!
 

pastorbud

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Just watched this. Lotta new info there for me.

Is this how most people do this? The other videos I watched did it differently.
 

racerone

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Did not show nearly enough time setting / feeling the gauge in the actual bore.----That is the key element in using these !!
 

Fed

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Do gauges have different shaped ends depending on usage?
Rounded vs square cut, you know where I'm going.
 

racerone

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Telescopic gauges have a " domed " end.--------As far as quality is concerned I would rate the video presentation In post #50 as a 4 out of 10.-----Lots of room for improvement.
 

pastorbud

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Did not show nearly enough time setting / feeling the gauge in the actual bore.----That is the key element in using these !!

Yes, that part I get. I’m working on learning the “feel” you’ve explained earlier. I know I’m not doing it correctly now, or I wouldn’t be getting absurd results.

But this guy

1— sets or locks the pistons in place at a diameter larger than the cylinder diameter, then
2– inserts the tool off-kilter to get it in; then
3– uses a sweeping motion to bring the tool through vertical, then slightly past vertical, to force the pistons in.

I have been
1– putting the tool in unlocked, then
2– trying to use “feel” (or additional devices, like that flaring tool gimmick) to center it up and square it.
3— Then when I think (and hope and pray!) I’ve got it positioned right, I lock it, and tilt it a little to clear the cylinder walls and take it out.

It seems like his method will more likely get the pistons to self-center across the cylinder and thereby prevent under-measurements like I’ve been getting.

It’s worth a shot, I think.

I’ll still have to “educate” my fingers to sweep it and to measure it without nudging the tool’s pistons further in.

Like I said....worth a shot!
 

pastorbud

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Telescopic gauges have a " domed " end.--------As far as quality is concerned I would rate the video presentation In post #50 as a 4 out of 10.-----Lots of room for improvement.

The rest of us could sure benefit from seeing your experience in action. 🛠 🧰

Any chance you could post your own training video? 🤔
 

racerone

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No my skills are " old time skills "-------Not familiar with video posting.----Even have trouble with remote controls for a TV.------No coins involved either.
 

pastorbud

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No my skills are " old time skills "-------Not familiar with video posting.----Even have trouble with remote controls for a TV.------No coins involved either.

Well, I may make my own. And I think we all know how THAT’S gonna turn out.
 

pastorbud

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Tried it again today with the new method. Similar results......

At this point I’m gonna just clean it up and install the new head gaskets.

This all started with absurd compression readings and now I can’t measure cylinders!

I either have an old, tired motor that needs a rebuild, or an old marginal motor that hasn’t had a proper compression test.

I will try again to get the compression test right, and then I’ll decide to either rebuild this one, or repair one of my other project motors...for my project boat! (1980s Hydrasport 222 Bowrider)

I will let you know. 😶
 

oldboat1

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and it may run....Deo Volente. Recommend reading or rereading Zen and the Art of Motorcycle Maintenance -- probably a sermon or two in there, with illustrations from your outboard experience :).
 

pastorbud

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and it may run....Deo Volente. Recommend reading or rereading Zen and the Art of Motorcycle Maintenance -- probably a sermon or two in there, with illustrations from your outboard experience :).

Amen and amen. I’ve done a head gasket on a Force outboard, powerhead swaps, lower unit Re-seals on outboards and mercruisers, even did an engine swap on a Hyundai SUV.

But this project has been all clown 🤡 no circus 🎪 from the git-go.
 
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