115 Crossflow Bubbleback Port Damage- Need Input

[Traxion]

I've got a 95' Evinrude 115 Crossflow Bubbleback that had a piston ring failure on the #3 piston. The ring broke and was pulverized before blowing out the exhaust. All the ports on the cylinder got knicked up but the exhaust side is obviously worse. I have attached a photo of the damage (had to resize hope you can see it). I am concerned about the damage to the exhaust ports and whether or not it can be repaired. Right now my plan is to send the block off for boring, nobody local will do blind hole boring. Any input on the damage and if it is fixable??

 

[emdsapmgr]

Re: 115 Crossflow Bubbleback Port Damage- Need Input

You've got a common failure on your block. 1. The port damage may not be something that should cause you to junk the block. Many folks that open up the intake/exhaust ports on these blocks wind up filing away the some of the port anyway. If you squared off the ports on the block, most of that damaged section might actually be ground away in the process. I'd leave the rest. 2. You've got aluminum transfer (scuffing) from the piston onto the cylinder walls. You may be able to hone that away and install a stock piston. If the scuffing is too deep, you'll have to overbore that one hole, then get an oversize piston.

 

[Traxion]

Re: 115 Crossflow Bubbleback Port Damage- Need Input

Thanks for the input. I'm most concerned about the top/bottom of the ports, if too much grinding is done port height will be noticeably altered. What is done when they square the ports, isn't most of the work done at the corners and port height is not changed??

I was planning on boring regardless. But, even at .030 over there is going to be significant damage remaining to the ports. Just don't know if someone can chamfer that out and things will still work OK or not.

 

[emdsapmgr]

Re: 115 Crossflow Bubbleback Port Damage- Need Input

Yes, that's correct. The bottom of the port is not the issue. On the intake side the bottom of the port is not exposed, due to the piston. The top is important. I would not raise the port higher than the middle (center of the port.) You can square off the ports by expanding the port opening to the left and right of the center. The picture is of a ported 1979 85 hp block. I'd be careful not to thin the port bridges between the ports.