How far over can I bore my '73 Evinrude 115?

[Newboatowner]

I finally got it fired up but it backfires. Did'nt take long to shear the key way on the flywheel. Metal in the cylinders on the starboard side. Rings? This motor has already been bored over 30. I can get kits for 40, 44 and 64. I don't want to go too big, just enough for a fresh rebuild. Cylinders look pretty good though, could possibly get away without re boaring but I want to do it right. So how far can you go without risking damage to the cylinder walls from being too thin or overheating?

[Newboatowner]

Oh, and what is a common price I should expect a machine shop to charge me to re bore?

[gotboostedvr6]

i pay 25 a hole

[Freddie Webb]

It is 50 a hole here, and it sounds like you need to change your timer base. You can index the flywheel to be sure, but that's the only time I have had one backfire and shear the flywheel key. You could have a lean sneeze at idle that sounds like a small backfire but usually if it breaks something it's a reed instead of the key on the flywheel.

[Mark75H]

I've seen motors shear the key first, then backfire ... be sure which is the chicken and which is the egg

[roadkill636]

If everything is removed all the way down to the bare block, my local shop charges $35 for the first hole $25 each additional hole,the block better be supper supper clean or they will charge you another $50/$75 to hot tank it!!!

[Bruster]

Oh, and what is a common price I should expect a machine shop to charge me to re bore?

Sunnen Power Hone, $35/ hole. Same correct surface integrity as original, round, straight bores with perfect sizing.

[76baja18ft]

just besure u can get whatever size piston u think u need before boring.. 1973 was a bastard year .. up to 72 took one piston.. and 74 and up took a different one...Pistons arent real easy to find because it was a one year only deal

[Newboatowner]

Thank you fellas! I'm pretty sure I can get just about anything for the 73. A few things are hard to get like tilt/trim motor and such but at maxrules.com ..... they got tons of kits or individual part for the 73. Pistons std. 30, 40, 44 and 64 over. Which was one of my questions, how far over can you take these before you start causing more problems and going through motors quickly? Thanks again!

[k-man]

i ran into that problem witha 73 135 - the pistons look the same but the wrist pins are alot lower on the 73 than the 74 on up - the rings are both 3.5 thow - good luck

[76baja18ft]

i ran into that problem witha 73 135 - the pistons look the same but the wrist pins are alot lower on the 73 than the 74 on up - the rings are both 3.5 thow - good luck

been there done that too.. i have a 73 model 115...:rolleyes: