Worrying compression results HELP PLEASE

I know these aren't the best photos but this is what the cylinders look like when I remove the head. to inspect further i would need to remove head again and replace gasket. Do you think there is any glazing on cylinder walls? or do you think the cross hatchings have been worn away completely?

Thanks
 

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Dan208 said:
I know these aren't the best photos but this is what the cylinders look like when I remove the head. to inspect further i would need to remove head again and replace gasket. Do you think there is any glazing on cylinder walls? or do you think the cross hatchings have been worn away completely?

Thanks
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Those look glazed to me. Try the method I mentioned. You may get lucky, but tbh. the best course of action would be to have the the cross hatchings re-honed and new rings. I know you can buy sprung loaded DIY honing bit you can use in a drill but I'd really avoid that. Having them rehoned by a pro shouldn't cost more than a few shillings if you just take the wetliners to him. Or better yet see if you cant get new pistons and liners in a kit. It's a simple enough job to replace.
 
BruceK said:
I see you can still get pistons and /or rings etc for it but although yours look like wetliners the various parts diagrams dont show any with wetliners so on that score I may be wrong. I'd still de-glaze and rehone them though.

Get your serial number and then go here for part numbers

Mercury Outboard, Mariner & Mercruiser Parts Online & For Sale | Crowley Marine
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If i opt for a re-hone will i need oversized rings or could i just use standard sized rings? Thanks
 
Before they rehone they will measure the top, centre and bottom of the cylinder for tolerance. If it's within spec i.e. no rebore needed then normal rings will be fine. Honing cuts are about 0.0025" into the cylinder wall. They will advise your course of action.
 
Brilliant i will make some phone calls tomorrow and enquire about this, i will keep you updated on the progress, cost and results. Thank you so much
 
BruceK said:
Those look glazed to me. Try the method I mentioned. You may get lucky, but tbh. the best course of action would be to have the the cross hatchings re-honed and new rings. I know you can buy sprung loaded DIY honing bit you can use in a drill but I'd really avoid that. Having them rehoned by a pro shouldn't cost more than a few shillings if you just take the wetliners to him. Or better yet see if you cant get new pistons and liners in a kit. It's a simple enough job to replace.
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Do you think i could remove power head and take off the barrels and set away with either a scotch bright pad or wire wool...remove glaze and put in new standard rings? As im looking online and oversized rings are not available anywhere neither are oversized pistons to go with it, every site i go on says "item unavailable", unless a slight rehone could allow me to use standard sized rings without piston slap i think my knly option it to remove glaze and cross all fingers it works...what you think?
 
I have deglazed bores using wet and dry paper, you need half an idea of what you are trying to achieve. If there is no wear lip at the top of the bore you should get away with deglaze and new rings. You need to gap them correctly and you need to check the wear in the piston ring grooves.
 
gordmac said:
I have deglazed bores using wet and dry paper, you need half an idea of what you are trying to achieve. If there is no wear lip at the top of the bore you should get away with deglaze and new rings. You need to gap them correctly and you need to check the wear in the piston ring grooves.
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Is the wear lip a ridge at the top of the piston stroke? Like the lip on an old brake disk?...cheers
 
Im not convinced about wet sanding either. You are after opposing spiral strokes at 45 to 60 degrees. To achieve that sort of precision by hand would take the skill of an oldskool artisan of which few are left and especially over the ports where it'll all start going wrong. Why try it. You have to take them off to do it, may as well pay your 30 odd quid and have them done by machine. Or, trust in a bit of luck. Try the brake cleaner, atf, seafoam combo first, or at least a few hard high load runs on seafoam first if the head is back on and see where you're at.
 
Brilliant thanks going to order some seafoam tomorrow and hoping to give it a hard blasting at WOT the next available flat calm day. Then il repeat the compression test and see if rings are sealing better. If not looks like im stripping head off and seeing if a machine shop can repair the cross hatchings without taking too much material from bores as like i stated above, the oversized pistons and rings are not available anymore just standard size ones, so i need to try to keep as close to factory spec as i possibly can. Thanks i will give all this a shot and report back with my findings
 
Just check they arent wet liners because to me they look like wet liners which will also explain why there are no oversize piston and rings.

i.e. a piston kit will include piston, rings, gudgeon pin and wet liner
 
Bruce is correct, they are glazed.
They do have a step at the top of the bore so stepped rings are the way to go.
It may be possible to hone a small step out, depending on wear and step size.
All engines have oversize or rebore sizes and if they dont they are wet linered, and even some wet linered engines have overbore sizes.
 
Just a thought...if my "wet test" compression readings in cylinders gives me 120psi then would it give me the same 120psi under normal running as the cylinder will be " wet" with oily fuel with every revolution of the combustion process when out on the water. If this is correct then surely 120psi compression is perfectly normal and WELL within specs of an old 2 stroke?. Id rather make sure 100% that i definitely have a problem before i start a rebuild that is going to be a long and expensive process. Cheers
 
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