1987 Mercury 70 hp low compression?

[flyingscott]

Where are you located

 

[dantheACman]

Dayton Ohio

 

[dantheACman]

With lifetime warranty 1495

 

[flyingscott]

With lifetime warranty 1495

That is not bad at all

 

[dantheACman]

I took the power head apart to get it ready to ship off and decide to remove the crank and now that I have power head apart I have done all the hard work this is really simple to me a 25 year refrigeration tech I rebuild compressor way more complex than this I just never took to many 2 stroke a parts any way I found local place that will bore and hone my question which should I buy a whole rebuild kit or just Pistons the bearings look and feel great two of the three piston look rough cylinder wall not bad at all I can fell a slight grove with finger but not really not that bad if I had to guess I would say a 100th of inch or .010 I just don't want to be lazy but I can't see any reason to replace bearing what you guys think and also wsm piston or wiseco piston and where is the best place to buy piston and or rebuild kits

 

[racerone]

Pistons are the first to suffer.-Crank and bearings are very tough on outboards.-----Most times they can be re-used with no problems.---Make sure you find the cause of the failure or you will be doing the job again !

 

[dantheACman]

No Title

I just bought the engine my guess from looking up online is the failure is from it was a oil injection motor and someone bypassed or did away with so it's from lack of lubrication it only a guess or just was used a lot I'm going to post some pic see what you guys think

 

[dantheACman]

But the strange thing bottom is worse the middle not that much at all top one

 

[dantheACman]

Got motor back from machine shop starting rebuild what should I use for holding needle bearings together can I use any kind of assembly lube or does it need to special manual says Mercury needle bearing assembly lube and no other go opus but I can't find it very easily any suggestions would be greatly appreciated

 

[dantheACman]

Rebuilt power head carbs new spark plugs rebuilt fuel pump new water pump I have broke in about 6 hours runs like a champ way more power than before so I decide to do compression test again I had it bored .030 wsm piston complete rebuild kit it was actually something I like doing I'm always working something with my trade and this was fun I used Johnny evinrude needle grease it was just overpriced Vaseline anyway to the point I checked compression again expecting hi numbers no I built a really cool compression tester using digital gauges very accurate I couldn't believe it 83.7 82.9 80.7 I don't understand so my stroke is 5.5:1 just thought I would up date

 

[dantheACman]

I'm still in break in process so I have not held at wot for over a minute but wot to get on plane and always changing rpms using 32:1 mix spark plugs look good got the old boat up to 36 mph at 4750 rpm 13.25 x 19 prop I just confused on compression any thoughts