1990 Evinrude 70hp vro fried cylinder

[Philby]

Ok<br /><br />Fried number 2 piston and scored the bore. Question is, do I need to bore out all three , or is it ok just to do the one.<br /><br />Somebody told me it would unbalance the engine .<br /><br />True or not ?

 

[Dhadley]

Re: 1990 Evinrude 70hp vro fried cylinder

You can bore one if the others measure in spec. Your machine shop will use a dial bore gauge to determine that.<br /><br />Dont forget to do all the updates and richen up the middle carb in the mid range also. Remember -- Champion plugs only!<br /><br />Good luck!

 

[Philby]

Re: 1990 Evinrude 70hp vro fried cylinder

Thanks Dhadley.<br /><br />Took the block to the machine shop today. For the cost of two cylinders I have decided to bore out all three. Having to go to .0030 to clear the grooves.<br /><br />My worry is I still don't know what caused the problem. Number two carb is clear as a bell so I can't see that it ran lean. It does have a three wire VRO, but that has been drawing oil fine. The other two cylinders ar as clean as a bell.<br /><br />I'll change the water pump while I'm at it, but again there was plenty of tell tale.<br /><br />The cylinder is fried on the exhaust side. Any ideas ?

 

[Dhadley]

Re: 1990 Evinrude 70hp vro fried cylinder

The oil pump is not the cause. I would bet that you were cruising in the mid range, probably around 4000 to 46000 when it stuck. Those motors tend to run lean in the mid range and the middle cylinder is the hottest on the 56 cid motors. And the exhaust side is the hottest. Thats why we richen up the mid range on at least the middle carb. And again -- stick with Champion plugs. We dont want any additional combustion heat in that motor.<br /><br />I'm sure you mean you are boring to .030 -- it wont clean at .020? Or at least two at .020?<br /><br />Good luck!

 

[Philby]

Re: 1990 Evinrude 70hp vro fried cylinder

Thanks Dhadley<br /><br />Spot on with the rpm. You wern't in England that day were you ?<br /><br />Philby

 

[seahorse5]

Re: 1990 Evinrude 70hp vro fried cylinder

There were a series of service bulletins about jetting, timing, and cooling that may have pertained about that year. <br /><br />The factory water pump kit is heavier duty and contains a stronger spring for the thermostat. There is also something about a different exhaust cover and relocating the water tell-tale fitting. Find a dealer that has been in business a while and will have the older bulletins.

 

[Dhadley]

Re: 1990 Evinrude 70hp vro fried cylinder

No -- haven't been to England. Yet. But yours isnt the first to do that either. <br /><br />Heres a little more detail -- in the mid range the motor is running at full timing and little fuel. That = higher combustion heat. (The middle cylinder, on that design, runs the warmest anyway. All motors have certian cylinders that run hotter than some others. That may change with rpm too.)<br /><br />Anyway, at that throttle setting the combustion temp (not necessairly the cooling water temp) slowly rises. The piston swells beyond specs and you know the rest of the story. <br /><br />As it goes back together and you do the up dates (as per the E/J bulletins) richen up the mid range jets also. Keep in mind (I'm sure your dealer knows this) that on some carbs the mid range jet is an air jet. Since it meters air, not fuel, you have to go smaller to go richer.<br /><br />And stick with Champion plugs! Personally I prefer the QL77JC4's. They're a pretty cool plug. With the rejetting you (or the dealer) may have to test to get her dialed in but its worth it.<br /><br />Good luck!

 

[pbailey]

Re: 1990 Evinrude 70hp vro fried cylinder

Is there a place one can get the bulletins for J/E engines?<br /><br />pbailey

 

[Dhadley]

Re: 1990 Evinrude 70hp vro fried cylinder

As Seahorse mentioned, your dealer will have them. I doubt he'll give you a copy but he knows the upgrades. <br /><br />Did you ever mention what spark plugs youre running?

 

[Rvfireman]

Re: 1990 Evinrude 70hp vro fried cylinder

Philby,<br />Got the same problem fried #1 and #2. Called local dealer--said to bring the motor to them and would fix it, and did not want to give out info on bulletins. bored .030 also. <br />Hope you have better luck than me.<br />Rvfireman

 

[Philby]

Re: 1990 Evinrude 70hp vro fried cylinder

Running champion QL77JC4. Fuel was as fresh as it comes. Thinking about it, at the end of last season I heard a slight knocking. Could this have been detonation ? I have to admit I didn't put fresh plugs in. <br /><br />Is rejetting an absolute necessary or precationary ?

 

[Dhadley]

Re: 1990 Evinrude 70hp vro fried cylinder

Good choice on plugs. What you heard last season could very well have been the start of this. <br /><br />No, you don't have to rejet or change anything. But how many times do you want to go thru this?<br /><br />BTW -- whats it propped out at? In the low to mid 5000 range?

 

[Phil B]

Re: 1990 Evinrude 70hp vro fried cylinder

Just to update on this.<br /><br />Bored out all three cylinders and rejetted ( that was suprisingly cheap ) A mechanic re built it all and did a really good job.<br /><br />Disconected the VRO because I couldn't stand the thought of it going on me.<br /><br />Result is ... better than ever. It idles, it accelerates, it dosn't smoke.<br /><br />Thanks for your help