boring cylinder

[caper_45ca]

My 1995 johnson 90hp mod # j90tleor recently broke a ring on the cylinder below #1 ....wall is scored a little....thinking I have to bore out and use oversize piston.....my question is this just the standard method of boring or are these cylinders chrome plated or something?...also other 3 cylinders checked out b4 we took head off at 120 psi in all 3....motor has less than 100 hours on it I am told....is it necessary to rebuild whole powerhead or just this one cylinder?...head also has some dents in it from the ring ending up on top of piston....do i need a new head or just grind the marks out....thank you 4 the help

 

[Dhadley]

Re: boring cylinder

You can bore only one if the others fall within spec. Youll only know that after you take the motor apart and measure it. <br /><br />To be correct you'll want another head. And make sure its a matching one to the port head. Dont worry about the starboard (damaged) head. It may or may not be a matching head. Get another head thats one number higher than the existing, goo port head.

 

[caper_45ca]

Re: boring cylinder

Thank you Dh for the reply...are these engines just the standard bore or do they have sleeves or some sort of special honing procedure?...when I l;ooked inside the cylinderr with the head off it appeared to b highly polished>>>.ty

 

[Dhadley]

Re: boring cylinder

Its just a steel sleeve in an aluminum block. Its 3.500" standard bore. Oversize pistons go from .020, .030, .044 and .064 so you have quite a range.<br /><br />Make sure that when you chose a machine shop to chose one that bores outboards. Not a shop that does automotive unless they normally do outboards also. If you need help in chosing a marine machine shop let me know. We can direct you to several that are very good. <br /><br />If it broke a ring, and it sounds like it did, we need to look at the set up when its back together. If it was lugging before and nothing changes, itll do the same thing again before the next 100 hours.

 

[caper_45ca]

Re: boring cylinder

thank you DH......It was definitely lugging and the ports and piston heads r full of dark tar like substance and some very hard carbon deposits....anyway does this cylinder go all the way through or does it stop at the bottom and have a slot in it for the rod to come thru....reason 4 asking is I was talking to a guy who has bored many engines ...I guess the local expert and he asked if it was all way thru or a slot????....i dont know cus engine is not apart yet...also u mentioned you know of some good shops for boring...do u know of any in Canada....and as soon as this thing gets bk together I will be posting looking for help in the setup to get rpm up...ty

 

[Dhadley]

Re: boring cylinder

Yep, it has the floor with a slot in it down by the crank. If the guy had to as that, you need another machine shop.<br /><br />Outboard Rebore in Canada is very good. I can find out his address if you like.

 

[caper_45ca]

Re: boring cylinder

thank you Dh...that would b a great help

 

[Dhadley]

Re: boring cylinder

I'll find out in the AM and post back.

 

[Dhadley]

Re: boring cylinder

Where are you located?

 

[caper_45ca]

Re: boring cylinder

I am in Nova Scotia...but wont matter have to ship the powerhead anyway.....

 

[Dhadley]

Re: boring cylinder

No problem. I'll let you know tomorrow.

 

[Dhadley]

Re: boring cylinder

OK, heres what we have --<br /><br />Outboard Rebore - 204-222-3782<br />Canada Marine Services - 705-745-5556<br />Marine Medics - 705-652-6731<br /><br />Hope that helps!

 

[caper_45ca]

Re: boring cylinder

Thanks for the info....going to the dealer tommorrow to ck on progress then contact the machineshops...keep u posted....thanks again