1986 70HP EVINRUDE SEIZED

[KennyBradley]

Hi,<br /><br />I have a 1986 70hp VRO Evinrude. While crusing at WOT she suddenly lost power and there was a rattling noise but she continued to run. I discovered she han no compression on no.2 cyl. Looking back I think I noticed she had been marginally down on power for the last couple of trips but it was't enough to worry me.<br /><br />On stripping the engine down I found no.2 bore badly scored, the piston was in a terrible state and the top ring had broken up and come away from the piston.<br /><br />I had assumed The reason for the early drop in power was a cracked ring which eventually broke up and caused the failure? All cooling passages where in good nick and the water pump was running well.<br /><br />Speaking to a parts dealer he said blocked main jets is a week point on these engines and if she ran lean the piston would seize before the bearings failed?<br /><br />If she had seized due to lack of lubrication Would she seize solid and stall or would she still be able to run on as she did.<br /><br />Any opinions would be greatly appriciated.<br /><br />Cheers Kenny

 

[OBJ]

Re: 1986 70HP EVINRUDE SEIZED

If it had stalled on a lack of lubrication, then all the cylinders would be in a terrible state. Most likely, the #2 carb had some crud in it running the #2 cylinder lean. Loopers hate lean. Your Tacho, if you have one, should have given you the "heads up" early on. A lack of power should also be a sign that "something" is amiss. Sorry ta' about your malady...."stuff happens". Hope you can get her fixed back up.

 

[Joe Reeves]

Re: 1986 70HP EVINRUDE SEIZED

Ken.... Fouled carburetors, and runing a engine on same, are the major cause of engine powerhead failure. The fixed high speed jets become somewhat clogged with the result being that the proper fuel mixture can not be delivered at the higher rpms.<br /><br />This results in improper lubrication, leading to piston failure, snapped/broken piston rings, scored cylinder walls, etc etc.<br /><br />And yes, one carburetor could have been fouled moreso that the others which would account for the one piston failing. However, upon rebuilding clean, rebuild and restore all carburetors to their factory specifications.<br /><br />In your case, you stopped using the engine while it was still running. If you continued to run it, it would have seized up guaranteed!<br /><br />Keep in mind that ignition failure could also lead one into that type failure but that doesn't sound like you encountered that. However, upon rebuilding, make sure that the ignition/spark is perfect.

 

[KennyBradley]

Re: 1986 70HP EVINRUDE SEIZED

Thanks for the replys guys,<br /><br />Unfortunately I don't have a tach, maybe I should think about fitting one?<br /><br />As it happens I had just rebuild the carbs a couple of months before this happened, hope I didn't do anything wrong?<br /><br />I will chack the carbs again. Apart from a blocked main jet, low float bowl level of air ingress upstream of the carb is there anything else I should look out for which may cause a lean condition?<br /><br />I've just had a look at the card in question and see no evidence of a blockage or anything gummed up. <br /><br />The main jet is the brass tube which goes into the venture behind the buterfly and extends about an inch into the float bowl, right??? It has three small holes in the side of it and another narrow tube inside it which extends all the way to the top of the carb???<br /><br />Thanks again Kenny.

 

[Joe Reeves]

Re: 1986 70HP EVINRUDE SEIZED

Ken.... No offense intended here but I'd suggest that you obtain a service manual to avoid any future expensive errors.<br /><br />The fixed brass high speed jet is located in the bottom center portion of the float chamber, in back of that drain/access screw/bolt that you see in the front of the float chamber.<br /><br />The area you're speaking of pertains to the low rpms and has nothing to do with the high speed.

 

[KennyBradley]

Re: 1986 70HP EVINRUDE SEIZED

Joe,<br /><br />No offence taken, I have the Clymer manual but I was looking for "main jet" rather than "high speed orifice" The online parts diagram only refers to it as an orifice. Sorry, My bad.<br /><br />Am I right in saying fuel from the float bowl is metered by this orifice before being drawn up into the venture by the tube I was speaking about in my last post?<br /><br />Just been and had a look at the high speed orifice and It was spotless.<br /><br />Are there any other things I should be looking for which may cause a lean condition.<br /><br />Thanks again, Kenny

 

[Joe Reeves]

Re: 1986 70HP EVINRUDE SEIZED

If the carburetors are absolutely clean, fuel/oil should flow thru them properly.<br /><br />A thought..... check the spark (spark plugs out). Spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!<br /><br />If poor spark on one cylinder, that would result in unburnt fuel in which case eventually would lead to the gasoline overcoming the oil mixture. This in turn results in what most mechanics refer to as a "Washout".... too much gas, not enough oil results in extreme friction which in turn tears the piston up bad.