EVINRUDE 120HP

[CYJMI]

HI ALL<br />engine is an evinrude 120 HP -1992-VRO<br />Decided to go for the big trip and took it all apart because it was "collapsing" after 2500 rpm and we checked everything we could before. The mechanics told me to check the little blades that are behind the carb , which I did-They look perfect except one of the four "windows" of that aluminium case was all black whereas the others are perfectly clean. So I took the piston out and except the fact it is also very black as compared to the others it looks (to me at least ..) perfectly allright including the rings ...sort of afraid I did all that job for nothing :-((.please tell me I'm wrong ! and what can be the diagnosis ?<br />many thanks<br />jm

 

[rickdb1boat]

Re: EVINRUDE 120HP

Did you check the compression on that cylinder before you tore it down? Rings could be shot allowing excessive oil blowback. Could also be from lack of fire to the plug on that cylinder causing the build-up on the piston.

 

[93bronco]

Re: EVINRUDE 120HP

how did you make out with this? i would like to know. thanx

 

[CYJMI]

Re: EVINRUDE 120HP

Continued...<br /><br />So the baby is totally dismantled and ...nothing apparently wrong whether on the N° 2 piston or cylinder.... I am getting nuts <br />The shaft ( is it the correct word in English?) seems just out of the factory , except all the area close to the N°2 piston is all black- I think of a bad combustion on this one. Is it possible that the electronics doesn't feed properly , just one of the plugs ??<br /><br />thx again bye<br />jm

 

[93bronco]

Re: EVINRUDE 120HP

i really wish i could help with this one. im working on what is supposed to be a 1988.<was told it was a 1992> it looks as if it was put together with 2 to 3 motors to make one. so i understand your frustration. but while you have it apart i would get new bearings to install with the new rings. i havent priced new reed valves yet but if you go to boaterssupply.com that site is an outstanding reference for prices and what ever else you might need.

 

[OBJ]

Re: EVINRUDE 120HP

CYJMI....hard to diagnos a problem without a little more info. When you say it would collapse after 2500rpm, is this to say it would not go higher in rpm or when you would get it higher it would slow down to 2500rpm? Did you get any type of warning alarms to indicate any problems? Since you have it torn down, are any of the rings stuck or any cylinders scored? Take the reed cages, these are the little blades you spoke of, and look through the back side of the cages. You should not see any light come through the blades as they rest on the cage or very little. Let us know what you find.

 

[CYJMI]

Re: EVINRUDE 120HP

first wanted to thank rick, Jim & 2k for their concern. several answers<br />- compression rates: the mechanics told me he checked that before and it would (slightly) go down on this piston when the engine gets hot ...<br />- collapse ... what happened in fact was that the engine would run perfect at iddle, then when you go at sea , step on the gas it would go to a complete halt at roughly 2500 rpm. I mean it stops and it is hard to start it again. Surprisingly if I injected gas with the choke I was able to prevent it to stop ...<br />What did we do after ...I bought a new VRO (don't tell you the price in France !!), put a new gas tank...new plugs. 2or 3 mechanics checked it and remained puzzled. I had found 2 buyers for this boat and missed the sale of course )<br />reed: I checked them visually (maybe should double check...).<br />let's hope !!<br />jm

 

[OBJ]

Re: EVINRUDE 120HP

JM....What the mechanic said about the compression falling when the engine warms up would nearly indicate stuck rings on the pistion. As the cylinder warms and expands, the rings being stuck would not expand with the cylinder. Thus the compression would fall. This could explain the reeds being black from carbon. You said that if you would inject full using the choke solenoid the engine would not stall. This indicates fuel supply problem. A new pump and the problem persisted. Which cylinder had the darkened piston and reeds? Give you some help here. Looking at the back of the engine, the cylinders on the left are the even cylinders, #2 and #4 top to bottom. Likewise. the cylinders on the right are odd, #1 and #3, top to bottom.

 

[CYJMI]

Re: EVINRUDE 120HP

hi Jim<br /><br />according to your classification it would be #2<br />(it is also the second starting from the bottom of engine..)-Regarding the rings I could not swear they were stuck when I put the engine apart. Anyway I thoroughly cleaned the "holes" the rings sit in and they seem to play absolutely free now ( still wonder if I am going to put new rings when I reassemble ??)<br />What amazes me (but not my mechanics) is that the aluminium part of the casing,where the middle shaft bearing sits seems all scratched. I wonder what by , since this part is not supposed to move ...(it is the bearing in two parts hold by a clip)<br /><br />thx for your help <br /><br />jm

 

[OBJ]

Re: EVINRUDE 120HP

CYJ....always put new rings in. If the cylinders are not scored, hone and replace the rings. Make real sure there is no carbon left in the piston ring grooves. If possible, check the cylinder bores with a micrometer to make sure they are not out of round. On the VRO pump, look for the hose that comes from the front of the pump and attaches to the block. Somewhere along the hose or attached to the block will be the pulse limiter. It is a fitting about 1" or so indiameter and one side will be blue. This should have been changed when the new VRO pump was installed. If the limiter is screwed into the block, take it out and see if there is any obstrucions in the part that attaches to the block. Some limiters have barbed ends on both sides and attach somewhere in the hose line. In either case, make sure the limiter is free from obstructions. You can't look through it because of its construction. It acts somewhat like a two way check valve. You should be able to blow through it from both ends. As for the scratches, I not sure what to tell you about them without seeing them. Look real close around the inside of the block for the possiblity of something coming lose and bouncing around inside.

 

[CYJMI]

Re: EVINRUDE 120HP

thx obj<br /><br />I ll get the block back after they bore the cylinders and try to reassemble all that next sat<br />( ...so many screws & bolts . Thanks for your last post ;, i'll print it and will learn it by heart and double check everything ... Since I am going to try to sell this boat i did not want to burn cash but you convinced me and I think i'll change the rings.<br />Btw thx also for helping me to improve my mechanic English I'll keep you posted<br />jm