maximum spark for 140

[tony120]

my 140 is an 85. max spark says in the manual 22 degrees.the machine shop says they retarded the timeing to 18 degrees.I know detonation is very bad..hence the word, but , is there anything to gain by checking timeing and going maybe to 19 or 20 slowly? I've read here some 140's rev over 7000 rpm.mine tops out at 5800 with a 15 by 17 prop.40mph GPS. 18ft center console. 87 oct fuel 50:1. only a thought.

 

[Dhadley]

Re: maximum spark for 140

Yes, the 1985's were to be set at 22. Since you mentioned a machine shop we assume its just been rebuilt. Why and was the cause found and fixed?<br /><br />Good choice on fuel and rpm. What spark plugs are you running? Are you running the airbox and cover?

 

[rickdb1boat]

Re: maximum spark for 140

FYI, Looks like QL77JC4 would be the correct plug for that motor..

 

[tony120]

Re: maximum spark for 140

plugs are QL78YC.yes the cover is on.i was told it had a scored cylinder,that was reboared.i looked into the cylinder from the spark hole and indeed one was reboared 20 thou.then of course new rings and bearings.now that she is broken in,i can wind her up to 5800 rpm.i only do it momentarly.she just purrs now.was just wondering why retard the timeing 4 deg? my old 120 ran good,but not this good.

 

[tony120]

Re: maximum spark for 140

my question still remains,why is retarding the maximum timeing 4 degrees benificial.the motor is running great because of this site.i bought a evo/john, factory manual,that i found here. did my own link/sync. a great idle i got.and thats what i was looking for.my question was never answered, " that the factory maximum timeing said 22 deg, mine is 18. can i gain anything by to 19-20".or will it hurt the motor?

 

[DJ]

Re: maximum spark for 140

I think Dhadley answered your question. It is to be set to 22.<br /><br />I think I would be asking the machine shop why they set it at 18?

 

[Dhadley]

Re: maximum spark for 140

The 78's are OK but I'm with RB, I'd opt for the cooler 77's. <br /><br />The book calls for 22 on a factory 1985 140 motor. If a rebuilder sets it back, thats up to him. There may indeed be a reason why he set it up that way. (have you checked it with a light at 5800?)<br /><br />I would not change it myself if it were me. I would take it to him and ask why its set back and can it be set up? If he says yes, I would have him do it.

 

[Dhadley]

Re: maximum spark for 140

Sorry DJ -- I type too slow.........<br /><br />Didnt mean to repeat.

 

[Paul Moir]

Re: maximum spark for 140

This is more of a question than an answer, but I've heard of some rebuilders retarding the timing for the break-in period. Mabey this is what's going on?

 

[tony120]

Re: maximum spark for 140

so what would i gain from advancing it from 18? more speed at wot? out of the hole faster? I know that sounds like a prop question but its an ignition Ques. as far as the plugs goes.there was a post here that said the jc4's were replaced with QL78YC's.sorry if I didnt rebuild this motor myself. the way i look at it, the motor runs great. but machine shops only build/rebuild,they arent tuners.a guy here says he can ring his 140 to 7800. I dont want to do that but wheres his max timeing at?

 

[Hooty]

Re: maximum spark for 140

Did he adjust the time with the engine at 4000+ rpm or with the timing ring against the stop and just spin the engine with the starter. If it's the later procedure, it should have been set at 18* btdc.<br /><br />c/6<br />Hooty

 

[tony120]

Re: maximum spark for 140

your missing all my other posts.it has nothing to do with the machine shop.the motor runs fine.I know what your saying.i did extencive searches about this here.I found one other website that said "retard the maximum timeing 4 deg".but WHY!i know car engines have valves,and i understand them.outboards are different,I know that.but like cars, you cant tell me when they are built,every single evinrude idles at 0-4btdc.some like more some like less.same with total adv.I guess. no one has a clear answer.

 

[clanton]

Re: maximum spark for 140

The rebuilder retarded the timing, hoping the piston will not burn or stick until the warranty expires. The engine should run fine at factory spec timing, if set correctly, and verify at close to 5000 rpms. Timing was retarded on some older engines for the unleaded and low grade fuel, there is old OMC service bulletin with list of engines and specs for these engines. Headgasket had to be change on some engines to run 87, some engines could run 89 with timing retarded 4 degrees. I will check the list for your engine tomorrow.

 

[ledgefinder]

Re: maximum spark for 140

Your motor will run stronger with the 22 degrees WOT timing. The website "screamandfly.com" focuses more on outboard high performance, & they'd be able to discuss this stuff in more detail. I haven't messed with the timing on OMC loopers. On a Merc 50hp 4-cylinder, the holeshot seemed the same, but the upper midrange was stronger & the motor wound out better.<br /><br />As DHadley says, you might want to check with the shop to see what they think of bumping it back up - they may have had to mill the heads.

 

[tony120]

Re: maximum spark for 140

THANK YOU clanton & ledgefinder, finally an edicational answer.they are not the only ones ive gotten here.its endless, except for me on this topic.thanks to everyone,even if they only read posts like this,like I have done so many times before.I only want to be educated better so " I " can build a great motor,without having to feel like im asking a stupid question.thanks to every one