Compression loss 1999 Johnson 115 HP

[water-wheels]

Hi,<br />I have compression loss in #2 of my V-4 Johnson 115HP OB. 3x 125, #2 only 50. Fuel OK, sparks OK.<br />Considering rebuild. Have not opened the engine yet, but I forsee to find a broken piston ring or so, with:<br />1) no damage to the cylinder wall, or<br />2) damage to cylinder wall.<br />Cause? Oil feed? Who can tell me. Engine has 40 hours on it, no leaks, looks like brand new!<br />Option 1: Can I just replace the ring, and should I replace all rings (other pistons) as well? Honing recommended? What else?<br />Option 2: Drastic honing and maybe OS piston.<br /><br />First, I need to know what caused this, to avoid it happen again. Than, I need a good source for parts. Finally, I need a good service manual or info on what I can expect when taking it apart, and putting it back together again. Torques, timing, etc. <br /><br />Thanks in advance!<br />Rob

 

[Walker]

Re: Compression loss 1999 Johnson 115 HP

First you need to see what the damage is. With only 40 hours I don't imagine its carbon buildup. Pull the head.

 

[water-wheels]

Re: Compression loss 1999 Johnson 115 HP

That's what I am going to do this morning indeed. I imagine just a broken ring, but what could be the cause of that? Bad oil pump?<br /><br />Rob

 

[water-wheels]

Re: Compression loss 1999 Johnson 115 HP

Is there an on-line parts-source for boat engine parts, like there is www.partsnmore.com for bikes?

 

[Walker]

Re: Compression loss 1999 Johnson 115 HP

I think you're jumping the gun on the broken ring theory, but if you did break a ring the piston will be damaged too. A couple of options for pistons are Wiseco and Bombardier (OMC)

 

[water-wheels]

Re: Compression loss 1999 Johnson 115 HP

OK, opened the head, was indeed a broken ring. No damage to the cylinder or piston, so the repair is simple... Will replace all rings now, since the engine will be split anyway!<br />Thanks for your help!<br />Rob