Bore the engine?

Discussion in 'Outboard Maintenance' started by mboeder, Oct 31, 2011.

  1. Oct 31, 2011 #1
    mboeder

    mboeder I Love microskiff.com!

    121
    1
    343
    Ok I am rebuilding my powerhead (new rings and complete gasket set) on my Evinrude 15hp. Since I have it completely apart I am wondering what kind of gains I would see from boring it out? (they make .20, .30, and .40 over bore) Is this worth looking in to or just a complete waste? We used to bore out our dirtbikes back in the day and saw huge gains! But a boat engine?
     
    mboeder, Oct 31, 2011
    mboeder, Oct 31, 2011
  3. Oct 31, 2011 #2
    anytide

    anytide Administrator Staff Member

    4,086
    486
    1,938
    if you can get oversize pistons/ rings ?? -the $ could be high on that.
    if not hone it out anyways...
    good luck :)
    -anytide
     
    anytide, Oct 31, 2011
    anytide, Oct 31, 2011

  5. Oct 31, 2011 #3
    mboeder

    mboeder I Love microskiff.com!

    121
    1
    343
    Mallory and Weisco both make them. I don't need pistons just rings, but since I have the power head off and apart.... Any one know of any gains I might get? 2-3hp?
     
    mboeder, Oct 31, 2011
    mboeder, Oct 31, 2011
  6. Oct 31, 2011 #4
    noeettica

    noeettica Well-Known Member

    3,653
    99
    2,253
    not really worth boring unless the cylinder is out of spec .

    the shop doing the boring may not hold exacting tolerances and you would ending up worse off


    optimize what you have ...
     
    noeettica, Oct 31, 2011
    noeettica, Oct 31, 2011
  7. Nov 1, 2011 #5
    AfterHours2

    AfterHours2 Stripper in my own Mind!

    2,544
    133
    918
    Unless your cylinder walls are in bad shape and you have seen a drastic drop in compression then I would just leave them alone. You wont see a big difference in boring them unless your dealing with a larger and more tolerant engine. Just my opinion..
     
    AfterHours2, Nov 1, 2011
    AfterHours2, Nov 1, 2011
  8. Nov 1, 2011 #6
    mboeder

    mboeder I Love microskiff.com!

    121
    1
    343
    Cylinder walls and pistons are in great shape, surprising since the rings are completely shot! So I will just order new rings and call it a day.
     
    mboeder, Nov 1, 2011
    mboeder, Nov 1, 2011
  9. Nov 1, 2011 #7
    anytide

    anytide Administrator Staff Member

    4,086
    486
    1,938
    hone it out anyways...
    - :)
     
    anytide, Nov 1, 2011
    anytide, Nov 1, 2011
  10. Nov 1, 2011 #8
    Frank_Sebastian

    Frank_Sebastian Well-Known Member

    787
    2
    391
    Follow the instructions on the new rings and you should do well. (break down the glaze with a hone) Often an engine gets hot from lack of coolant water and the rings lose their tension. This results in low compression and poor running. A new set of standard rings can help a lot. It would be much better to trade the 15 for a 25 than to bore it looking for power.

    Frank_S
     
    Frank_Sebastian, Nov 1, 2011
    Frank_Sebastian, Nov 1, 2011
  11. Nov 2, 2011 #9
    Creek Runner

    Creek Runner Well-Known Member

    1,544
    21
    643
    Yeah Boring the cylinder, won't add performance without getting additional air into the combustion chamber. Which also will require additional fuel to keep from running lean.

    If the walls are good then hone and replace the rings.

    Tip: Any rebuild I do I always inspect the wrist pin carefully and Always replace the c-clips that hold the wrist pins in. The wrist pins are the most highly stressed part inside an internal combustion engine
     
    Creek Runner, Nov 2, 2011
    Creek Runner, Nov 2, 2011
Loading...
Similar Threads Forum Date
Bored? Fishing Reports Jul 3, 2011
Stuck Inside and Bored? Fishing Reports Jan 31, 2010
The i was bored project / Custom cooler Bragging Spot Oct 21, 2010
I'm bored so here is muh 2 bragging spots Bragging Spot Aug 4, 2008
SOLD/EXPIRED Bored looking for something to build..... Sold/Expired Classifieds Jan 2, 2010