Re Bored Evinrude 70, Carb Jet Change?

[bshellrude]

Hello All:<br /><br />Have a question I'd like to have answered.<br />Just in the process of rebuilding 1986 Evinrude 70 VRO. Had the cylinder walls bored with oversized pistons/rings.<br />Question is this, as the carbs use fixed jets and include no mixture adjustments, and according to manual can change jets to change mixture, will this be required due to the larger bore?<br /><br />Cheers,<br />Ben

 

[voodoo]

Re: Re Bored Evinrude 70, Carb Jet Change?

No. The displacement changed by an insignificant amount.<br />86 was a bad year for vro pumps, did you find the cause?

 

[Dhadley]

Re: Re Bored Evinrude 70, Carb Jet Change?

The larger bore will not affect the jetting but there were some bulletins out about jetting on the 56 cid model. <br /><br />What happened that caused the motor to need rebuilding and why?

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

I believe I found the problem.<br />First of all, upon rebuild, found that the bottom carb was slightly gummed up. Gave 'em all a cleaning + kit and put them back on. Which actually leads me to my next question, I've found a number of posts on mixture. Now my manual states that there is no adjustments on my carbs, however there is, on the throttle linkage (starboard) side, just above and towards the stern of the engine there is an adjustable jet. Is it true that all should be seated in, then 1.5 turns out... 1/8 turns in till sputter then back out 1/4... etc... etc...???<br /><br />Secondly, upon performing link and sync, found that the bottom carb (trouble cylinder) linkage was loose... so while the top two carb throttle plates were opening, the bottom was still ever so slightly behind. This problem fixed. Curious if this would have contributed? VRO functions on crank pressure/vacum right? So if engine RPMS are up, but bottom carb throttle plate is slightly more closed that center and top?... hrmmm... guess not, if anything would run richer right?<br /><br />Thirdly, since this happened at WOT, the rebore fellas were quite adament about WOT timing!!! Saying it is absolutely imperative that this be set correctly. Of course I won't be able to do this until engine is nicely broken in and have verified (as you say voodoo) vro pump functionality. Until that time, will pre-mix 50:1 and mark oil tank as is suggested by so many.<br /><br />Last but not least, the manual suggests that for 1986 70HP's, if used at sustained high-speeds, different plugs should be used (assuming cooler plug).<br /><br />Thoughts? Comments? Suggestions?

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Sorry Dhadley, didn't answer your question I guess.<br /><br />Blew out a chunk on the exhaust side of the bottom piston. Gauged the cylinder wall.

 

[Dhadley]

Re: Re Bored Evinrude 70, Carb Jet Change?

No, I think thats reasonable to connect the problems with the bottom carb to the piston damage. We'll continue to look just in case thats not all of the source but its good that you found what you did.<br /><br />Are you sure you have an 86 motor? The adjustable jets didnt show up on the 56 cid motor until 89. Its possible someone could have used a later set of carbs.

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Hmmm... that may be possible. It would explain a few descrepancies in the manual.<br />Hopefully torque specs would still remain the same???<br /><br />Even so, what are those jets? Assuming Idle mixture/slow speed jets?? If so, are the instructions that I've found correct (i.e. the above steps...)?<br /><br />Cheers,<br />Ben

 

[Dhadley]

Re: Re Bored Evinrude 70, Carb Jet Change?

That seems like a good place to start. What ever makes it idle the best.<br /><br />Whats the model number?

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Unfortunately don't have it handy. Only the serial #G02531922. Although I'd sceptical that would be of any use at the moment??

 

[Dhadley]

Re: Re Bored Evinrude 70, Carb Jet Change?

On Evin/Johny's the model number tells us what it is. No biggie -- whenever you get it.

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Ok, I've got the model number.<br />VE70TLESB

 

[marinemech]

Re: Re Bored Evinrude 70, Carb Jet Change?

1990 70 hp trim long there is a service bulletin about changing main jets and reducing timing advance to 17 degrees<br />there is another about moving the "tell tale" hose outlet from side of exaust cover to top of block <br />have your dealer look them up for you

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Thanks Mech. TO 17 degrees?? Really...<br /><br />Indication I got from the bore shop was that one degree of timing advance will increase cylinder temp by 2-300 degrees... So considering my timing should be 19BTDC (According to the markings on the engine)... that would increase the temp in the cylinders by quite a bit would it not?<br /><br />Can you remember, does the timing change need to be done in conjunction with the main jet change?<br /><br />Or even if you can remember the reason for the timing change? In the interim I will contact my dealer (there are few here in winnipeg) and see if any can dig them up...

 

[rdav13]

Re: Re Bored Evinrude 70, Carb Jet Change?

I just went through the same thing with my 60 horse. The service bulletin says to change the high speed jets to a larger size and retard the timing from 19 to 17 degrees. Both these should make the engine run cooler.

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Thnx for the info rdav! Much appreciated.<br />Question though... will this reduce HP/RPM capabilities as well?

 

[rdav13]

Re: Re Bored Evinrude 70, Carb Jet Change?

My engine runs as good or better than before. The timing change may limit Hp slightly but a long living motor is worth the trade off.

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Thanks for the info rdav.<br /><br />I've been in touch with the dealer and they are trying to dig up the service bulletins.<br /><br />And yes, long living motor is paramount!<br /><br />Cheers,<br />Ben

 

[bshellrude]

Re: Re Bored Evinrude 70, Carb Jet Change?

Having problems with the dealer.<br />Does any one happen to have the part number for the upsized jets recommended by the aforementioned service bulletins??

 

[rdav13]

Re: Re Bored Evinrude 70, Carb Jet Change?

I've got the bulletin at home & will post the number tonight.

 

[rdav13]

Re: Re Bored Evinrude 70, Carb Jet Change?

Got home and looked up my bulletin. #2271, Looks like it does not apply to your model year. It applies to 1991 and 1992 and certian 1993 60-70 engines. <br />In my case the jets in the calibration kit were two sizes larger than stock. The only other item in the kit was a sticker stating 17 degree max advance to apply over the old 19 degree sticker.<br />There is another bulletin, #2276 rev 1, which does apply to 1985 through 1994 70 hp engine which involves relocating the tell tale hose from the side of the engine to the top of the block. (prevents air from being trapped in the upper half of the cooling system).<br />If yours hasn't been changed, you may want to consider this.