Inline 4 cylinder timing and synch questions

[ozarkjeep]

I just read Clams good post on inlines.<br /><br />I have a 1970 80HP , it says direct charge on the sticker, sticker on engien calls for 27degrees max timing.<br /><br />I adjusted it yesterday for 5 deg at idle and 23 max.<br /><br />can I run safely on 87 octane fuel like this?<br /><br />I dont mind backing it down to 19-20 degrees if it will live longer.<br /><br />also, im unsure of my interpretation of the primary and secondary pickup setup.<br /><br />yesterday, this is what I did.<br /><br />primary starts to open throttle as soon as distributor starts moving, then secondary starts moving throttle as soon as the distributor stops moving. Is that close to right?<br /><br />I havent had a chance to test ride yet...<br /><br />thanks!

 

[Clams Canino]

Re: Inline 4 cylinder timing and synch questions

Sync is "close to right" <br /><br />21 degrees is safer. What you're dealing with is a 4 way "detonation disaster mix"<br /><br />Low Octane<br />High Load<br />Too Much Advance<br />Too lean mixture<br /><br />When any of those factors go against you, or *combine* against you, pistons begin to melt. Therefore.... setting max advace to 21 degrees gives you a little more breating room in the rest of the world.<br /><br />As for fuel... most pumps have 3 grades - the "midgrade" is fine if you have the advance at 21 and you're not overpropped. Just think "pinging = death" and your in the right mindset.<br /><br />-W

 

[ozarkjeep]

Re: Inline 4 cylinder timing and synch questions

Hey thanks Clam,<br /><br />I do understand a little of the detonation problems, Ive worked on a few jetski engines, you usually never hear it on them, just get hot and then rebuild.. haha<br /><br />Hey would you care to elaborate better on how to improve my "synch" technique? Ive got a an old seloc manual and its TERRIBLE, what I described in teh text is what I got from reading the info in the book.<br /><br />0.000-0.005" inch from contact between primary and throttle at 5-7 degrees.<br /><br />and then with distributor just touching spark advance stop screw, the secondary should just be touching.<br /><br />I havent had a chance to run it set like this yet.<br /><br />I hope it will be lightly loaded, its a 16 foot aluminum V hull, the 80HP should move it along pretty well, even detuned to run on 87 octane I hope.<br /><br /><br />thanks for your help!

 

[Clams Canino]

Re: Inline 4 cylinder timing and synch questions

Same with the inlines you don't hear it till it's mostly over. <br /><br />What the manual is saying is that as the advance is passing +5 degrees the first throttle pickup outta hit, then once the advance is maxed it's time for the second one to hit. <br /><br />Then set the final stop screw so that the STOP not the CARBS is what stops the throttle from any further movement when the carbs are wide open.<br /><br />Once that's all set... then it's time for "fun and games with idle mixture screws" in order to balance the need to troll without "loading up" vs having a decent hole shot. Bring a friend and lotsa beer for that part.<br /><br />Load can only be tested with a tach - it's the prop that counts as much as the boat.<br /><br />-W<br /><br />

Originally posted by ozarkjeep:<br /> Hey thanks Clam,<br /><br />I do understand a little of the detonation problems, Ive worked on a few jetski engines, you usually never hear it on them, just get hot and then rebuild.. haha<br /><br />Hey would you care to elaborate better on how to improve my "synch" technique? Ive got a an old seloc manual and its TERRIBLE, what I described in teh text is what I got from reading the info in the book.<br /><br />0.000-0.005" inch from contact between primary and throttle at 5-7 degrees.<br /><br />and then with distributor just touching spark advance stop screw, the secondary should just be touching.<br /><br />I havent had a chance to run it set like this yet.<br /><br />I hope it will be lightly loaded, its a 16 foot aluminum V hull, the 80HP should move it along pretty well, even detuned to run on 87 octane I hope.<br /><br /><br />thanks for your help!

 

[ozarkjeep]

Re: Inline 4 cylinder timing and synch questions

thanks for the info!<br /><br />the engine came from a 1970 LARGE ski boat... so I dont know what prop that would be, its got some dings, so Ill probably look for a replacement anyway..<br /><br />any suggestions on pitch for a deep wide Vee hull, that will spend time striper trolling and slowly cruising the lake are welcomed.