Ratio for extended Idle

[Barryvillegas]

I have a 1989 70 HP Jonson VRO but i disconnected the VRO pump, what ratio should i use for extended idle (trolling speeds). 50-1, 75-1 ?????

 

[phatmanmike]

Re: Ratio for extended Idle

50:1

 

[Dave Abrahamson]

Re: Ratio for extended Idle

Might also help to open up the recommended gap on the spark plugs from .030 to .040

 

[walleyehed]

Re: Ratio for extended Idle

Both of the above would be the proper combination.

 

[DHPMARINE]

Re: Ratio for extended Idle

I sugggest a sync&linc if you haven't done this recently.Too bad about your VRO.It adjusted the ratio for you.You can also try trimming up while trolling,less back pressure on the exhaust.<br /><br />DHP

 

[ob]

Re: Ratio for extended Idle

As DHPMARINE says,unless your old vro was kaput,the earlier year vro pump varied the ratio for you.I also highly agree and practice his last suggestion and trim the engine up when trolling for extended periods as long as the water I'm trolling in isn't too choppy.I also agree with the 50:1 mix and the .040" clearance of the QL77JC4 plugs if trolling for extended periods.All sound advice.

 

[jy118lfd]

Re: Ratio for extended Idle

Also if it has a recirculation system make sure the check valves are all working

 

[Barryvillegas]

Re: Ratio for extended Idle

O.030 to 0.040 inches?? centimeters? sorry if this is a stupid question but i always use metric units

 

[R.Johnson]

Re: Ratio for extended Idle

Who came up with the .010 extended plug gap? can I put this down as not to much grease on top of my drive shaft, or not storing my battery on a cement floor? Can I assume the older my plugs' get, the better my engine will idle?

 

[Dunaruna]

Re: Ratio for extended Idle

Barry, .040" (thou) is 1 millimeter (mm). <br /> .030" is .76 mm

 

[ob]

Re: Ratio for extended Idle

My understanding is that # 1 ,the earlier specs called for a .040" gap on the original plugs.#2 ,I was under the impression that at sustained lower speeds that combustion temps are kept to a lesser and that two cylcle oil residual would increase the likelyhood of gap fouling the plugs.An older plug doesn't just increase in gap as it ages and is arc worn ,but also the conductive components become fatigued.I'm wide open to any other view points.

 

[walleyehed]

Re: Ratio for extended Idle

By R. Johnson;<br />

Who came up with the .010 extended plug gap?

OMC did.....service bulliten came out in about 1984 or 85.

 

[BillP]

Re: Ratio for extended Idle

If I was trolling that vintage 70 omc all the time I'd run 100:1 and make sure the tstats were working. If memory serves right the VRO was 150:1 at idle and 50:1 at full bore.

 

[walleyehed]

Re: Ratio for extended Idle

The "economixer"....yep, Bill, 150:1 at Idle and 50:1 at WFO. OMC claims approx 80:1 at "cruise".

 

[BillP]

Re: Ratio for extended Idle

Originally posted by walleyehed:<br /> The "economixer"....yep, Bill, 150:1 at Idle and 50:1 at WFO. OMC claims approx 80:1 at "cruise".

My old omc friend told me they still have a wide safety margin at those ratios...But the corrosion resistant coating is too thin for sitting several months at 100:1 in high humidity.

 

[walleyehed]

Re: Ratio for extended Idle

Back in the days when our distributor was racing Johnson outboards, they took a 135 and ran it for several hours at all throttle settings with a 100:1 ratio of their own std oil, then tore down and inspected. all looked well, but they never had the engine setting more than a day or 2 during testing, and of course this was in the Loveland, Co area where 10-15% humidity is common-place in the summer.

 

[CaptainPuget]

Re: Ratio for extended Idle

I’ve owned several of these 70hp inline 3 motors over the years and it a great engine but one thing it doesn’t do well is idle. I suggest getting a small 4-stroke kicker for extended trolling. It will pay for itself in fuel savings.

 

[walleyehed]

Re: Ratio for extended Idle

to pay the difference in cost, it would have to be used about 700hrs a year...

 

[Dhadley]

Re: Ratio for extended Idle

Ive had lots of the 3 cylinder motors both the 49 and 56 cid models. They all idled for hours if needed. Some were premix at 50:1, some were VRO and some were oil injected.

 

[walleyehed]

Re: Ratio for extended Idle

we ran several of the tripples as well, and properly set up, Idle was never an issue for us either.<br />Now, I'm goin' fishing for 4 or 5 days, so play fair boys!