1993 75hp evinrude

[shoalrunner 350]

Hi i just rebiult my 93 75hp evinrude I had all 3 cly.bored 20 over 3 new wiesco 20 over pistons went through the normal brake in procedures double oil good water curculation motor never seemed to run hot ran great for about 1 and a half total run time hours and the middle #2 cylinder siezed up there was no damage what soever on the top of the piston and both rings were fine not broke any thoughts on what might have caused this its the first time i have had this happen.

 

[phillnjack2]

Re: 1993 75hp evinrude

what makes you think it siezed on the middle ?
and where did you get a 1993 75hp evinrude ?

Now if the piston has no damage at all and the rings have no damage at all then it didnt sieze on the piston or liner.
the siezure was probably on the crank or the wrist pin (gudgeon pin in england).
to be siezed would of been 1 or all 3 things
1/ major overheat ,either no or low water getting round the liner/head
2/ no loil low oil
3/ far too lean on that piston. (carb leaned out too much)

But to sieze up it would normaly damage a ring, even if just slight.
so find the problem and change the rings on that cylinder for sure.
check the cross hatchings for any of the slightest of marks as well.

then go find the engine number and let us know what year and horsepower the engine realy is.
a pic of the engine will probably do, as most folk on here know their engines very well.

coz i cant find a 1993 75hp evinrude,definitely not listed in uk or europe.
Last ones i knew of were late 1980's.


phill

 

[Faztbullet]

Re: 1993 75hp evinrude

Good ole Siezcos:facepalm:..... How did you break it in? What was your finished bore clearance? Did you relieve the exhaust bridge port?

 

[trendsetter240]

Re: 1993 75hp evinrude

Good ole Siezcos:facepalm:..... How did you break it in? What was your finished bore clearance? Did you relieve the exhaust bridge port?

Hey I resent that I rebuilt one of these with wiseco pistons and they worked great. You do need to warm them up slowly during the break in period because the clearance is only .003 (if your machine shop did it within spec).

I was warned after my rebuilds to let them warm up slowly at idle for the first 20 hours or so because the forged pistons can expand faster than the block and seize. Maybe that happened here but phillnjacks suggestions could be right as well. Gunna have to pull it apart to find out.

 

[shoalrunner 350]

Re: 1993 75hp evinrude

my bad it is a 1983 sorry bout that and there was damage to the sides of the pistons misled you there but the rings were not stuck and were not broke my thinking is improper bore I have rebuilt 15 to 20 of these motors and this is the first time this has happend. there is aluminum from the piston on the cylinder wall, this is the first time I have used this particular machine shop though.

 

[shoalrunner 350]

Re: 1993 75hp evinrude

sorry it is a 1983 and there is damage to the piston and cylinder wall it does lookas though it got hot but shortly before it locked up it went up to 6000 rpm i backed it off but it was turning 5200 at wot witch makes me think it really leaned out does that make sense to you. thanks for repling.

what makes you think it siezed on the middle ?
and where did you get a 1993 75hp evinrude ?

Now if the piston has no damage at all and the rings have no damage at all then it didnt sieze on the piston or liner.
the siezure was probably on the crank or the wrist pin (gudgeon pin in england).
to be siezed would of been 1 or all 3 things
1/ major overheat ,either no or low water getting round the liner/head
2/ no loil low oil
3/ far too lean on that piston. (carb leaned out too much)

But to sieze up it would normaly damage a ring, even if just slight.
so find the problem and change the rings on that cylinder for sure.
check the cross hatchings for any of the slightest of marks as well.

then go find the engine number and let us know what year and horsepower the engine realy is.
a pic of the engine will probably do, as most folk on here know their engines very well.

coz i cant find a 1993 75hp evinrude,definitely not listed in uk or europe.
Last ones i knew of were late 1980's.


phill

 

[phillnjack2]

Re: 1993 75hp evinrude

Well first of all 1.5 hours is not a lot of run time on new pistons rings and rebore.
i wouldnt take an engine to max revs for atleast 4 hours but that is just me.

Now if allumininium is on the cylinder wall then you have definitely got a heat build problem, could be the lean carb on the middle
but could also be poor water circulation, and poor re-bore job.
Like said above you need to check the clearances of the pistons etc as if the gap is too small then the piston will grow with
heat and stick again.

How bad is the piston ? can it be polished and then scratched up again so it keeps a bit of oil on the piston sides ?
you dont want polished only sides or they will not carry oil for lubrication and could end up melting in the bore if its gonna be tight.

I would be looking at the carb first, if it is a bit too lean then that could be the problem.
But you must let the engine warm up at idle for about 20 mins, and then take it very easy for few hours to let everything bed in properly.

any pics of the piston ?


phill

 

[shoalrunner 350]

Re: 1993 75hp evinrude

sorry dont have any pics the piston is in bad enough shape that it will have to be replaced I am going to take the block back to the shop that done the work and have him check it i do think it will clean up though but not sure will let you know what i find out probably nxt week.

 

[shoalrunner 350]

Re: 1993 75hp evinrude

could it have leaned out enough to have gotten 6000rpm out of it. thats has me worried unless the tack is bad but it was just turning 5200 which is good.