Retarded Timing

[DDAADDYY]

Just doing the finishing touches to my 75 merc 650. I've got the manual, and a timing light, don't have the pointer but matched the belt alignment up on the tab on the dist with the little indicator on bottom pulley then made a coat hanger pointer. I'm trying for the first time to set carb sync and right away noticed neutral idle is about 6 to 8 degrees ATDC!!!<br />This might explain the bogging etc, I've been dealing with. Starts perfect, idles good. After some bogging, WOT is good plenty of speed. Got a 14 pitch prop,14 foot deep V fibreglass boat and 074 main jets on thuroughly decarbed carbs. 1 and a quarter turns seemed to have done it for idle adj. Can too rich idle create bogging as well as too lean? Used to be 1 and a half before manual arrived. Took the powerhead apart and noticed lower reed block locating pin a little sloppy up and down around a sixteenth of an inch which in turn made the reed block go up and down too once installed. I'm going to replace this fall but for now the tech up here thought it be ok for now as once the other half torques down it'd be OK Little squeak that's it. I don't have a tach wish I did cause if I advance the timing any, way too many RPMs scare me. Do I simply take this thing out to the lake hook up timing light and idle in gear find 3 to 5 degrees BTDC tighten nut on spark stop and that's it? My flywheel has 2 degrees BTDC marked. Any reason for that and 23 is max advance<br />Thanks Real close

 

[emckelvy]

Re: Retarded Timing

The total and maximum spark advance is only adjusted with the throttle advanced such that the distributor is against the 'spark stop'. Recommend you run 21 deg BTDC instead of 23, your motor will last longer.<br /><br />If your TDC alignment mark is close, at idle speeds you're running WAY retarded. It should be closer to Zero (or a few degrees advanced) than 6 to 8 deg retarded. That much retarded would make the motor 'doggy', idle slowly/poorly, and might make it difficult to get enough adjustment in the spark stop to achieve full advance.<br /><br />You might try moving the distributor one tooth to the advanced side and see if that picks it up a bit. If it doesn't idle too fast, and your total spark advance is in the correct adjustment range, I'd leave it like that. Since you don't have the real TDC pointer it's certainly possible to have gotten off a tooth on the belt alignment.<br /><br />You'll want to rotate the distributor 1 tooth CCW (edit - Make that CW - Clockwise!!!! - ed) which would advance it in relation to the flywheel.<br /><br />Try that and see if it works better, I bet your timing at idle will be closer to zero.<br /><br />BTW, the belt timing is the only thing that controls initial timing at idle. The spark stop is only for maximum spark advance.<br /><br />The primary pickup is the point where the throttle butterflys start to move when advancing the throttle. If this occurs at the specified 3-5 deg BTDC, you have correct belt alignment and will be able to adjust your maximum advance too.<br /><br />HTH.............ed

 

[DDAADDYY]

Re: Retarded Timing

Thanks Ed, I didn't have the pointer when I re installed the flywheel so just used another reference ( a flywheel tooth next to the belt alignment line on flywheel in relation to nub on bottom pulley on dist. to mounting bracket). It worked, got it back to where it was before. Then made the pointer in relation to that. I bought this motor off a nice old guy who does nothing but rebuild these things in his backyard and am starting to wonder if he gave it to me a tooth out. Did notice the when light was hitting right in the middle of the cutout for the top cowl support, all the marks were way clockwise of the cutout hmmm. Give it a try and get back. I took it to the lake and couldn't get it to shift to forward without jumping on the two controls to keep it from stalling and a little past idle in gear, it's still 2 or 3 degrees ATDC. Could all this pain be from a tooth?? Wish I was a dentist ha!<br />Keep ya posted

 

[DDAADDYY]

Re: Retarded Timing

I tried that and got worse so tried two teeth CW<br />as opposed to CCW and it's now bang on 3 degrees BTDC wahoo, just launches when on muffs like never before. Goin campin and I think this is it. It'll be way easier to Link and Sync when I'm getting proper timing readings. Keep ya posted

 

[emckelvy]

Re: Retarded Timing

Sorry about that, you're right, turning the dist CW would make it fire sooner, not later. <br /><br />It was late last night and I had a rough nite of wakeboarding on the lake!!! lol lol <br /><br />Glad to hear that things are looking up. Now if I could just get rid of these sinuses...............

 

[DDAADDYY]

Re: Retarded Timing

Yeah that was it Ed, Holy smokes, this thing's pushin' 50 mph. WOT wahoo!!! I'm a chicken but my wife got to "SMELL" the water on the kneeboard nyuk nyuk. Now I'm gonna tear the powerhead apart again to fix that reed block assembly. The squeaking is drivin' me. New floats for the carbs are on their way and it turned out about 1 and an eigth turns from seated for the idle adj. for now anyway.<br />Thanks for the tip<br />Russ

 

[DDAADDYY]

Re: Retarded Timing

If your still there Ed could you please explain WHY the motor will last longer at 21 degrees as opposed to 23?<br />Thanks

 

[jfholijr]

Re: Retarded Timing

I second that question too. My manual also says to set max advance to 23 degrees.

 

[emckelvy]

Re: Retarded Timing

Gas nowaday's isn't what it used to be back when these motors were built. Timing had to be bumped back to 21 deg BTDC on the inline 6's in order to reduce the possibility of detonation. <br /><br />The 3-cyl is of similar construction as far as pistons go and if anything, is more highly stressed than a 6-cyl because of it's small displacement.<br /><br />Don't really hear a lot of talk about 3-cyl timing, because frankly, there aren't as many of them left compared to the 4's and 6's. But the same caveats apply:<br /><br />Use quality fuel; use quality oil; set the timing advance back to no more than 21 deg BTDC; and prop the motor to allow WOT in the high range of the power band. This reduces stress on the motor and may give it a longer life. You won't notice much diff in power between 21 and 23 but it will reduce the chance of detonation.<br /><br />Run some kind of carbon cleaning agent (Engine Tuner, Carbon Guard, Ring-Free, Seafoam) thru the motor at least once a season. This'll keep the rings happy.<br /><br />Anyway, this is based on many years of collective knowledge from a number of boating forums, take it for what it's worth, YMMV & IMHO........ed

 

[DDAADDYY]

Re: Retarded Timing

Thanks for the info Ed. I did have to rip the powerhead apart again to fix the reed block centering pin's wiggle with permatex bearing mount/sleeve retainer then torque'er all back up, double check timing and away. For primary pickup, I read alot about moving to "INITIAL SETTING" both Seloc and Merc manuals say this. Where is this? Is it next to the first ridge on the throttle actuator cam, or on top of that ridge right next to where the throttle really opens up? Hoping you can clear up this mud<br />I gratefully appreciate the tips. I'm thinking this flywheel is from a 4 cyl. as the #1 TDC. lines up to my coathanger pointer as do the timing settings with the timing light, but the BELT ALIGNMENT MARK is way off ah well, least it works<br />Regards<br />Russ

 

[jfholijr]

Re: Retarded Timing

Hey Mr. ED, I also have the same motor as Dad and I reset my Max Advance to 21 degrees BTDC. My result was that I lost around 200 rpms at WOT. From what I have read above this sounds normal, Correct? Do you recommend leaving it set at 21 degrees and simply have my prop adjusted to compensate for the rpm drop? Thanks

 

[emckelvy]

Re: Retarded Timing

What's that, about 1 mph of boat speed? If it didn't kill your hole shot, and you're still up in the WOT rpm range, you could leave it be. Or, go down 1 or 2 pitches; or have a prop shop remove some of the cupping on the propeller blades, which will raise rpm too.<br /><br />Re: the primary pickup, I'd adjust so the carb throttle plates "just" start to open at the specified deg. BTDC, if that lines up with the marks, so be it, but I expect the marks are just a reference point and you're more accurate if, from there, you eyeball the plates so you can watch them move.

 

[jfholijr]

Re: Retarded Timing

I'm not sure of speed loss, hole shot took a second longer but not biggy, so I'm gonna have prop adjusted.<br /><br />What would happen if the surfaced of the Throttle Lever Cam and Nylon Actuator Cam were to be worn down? Would setting the initial sync and then because the two surfaces are worn wouldn't that, as I increase throttle speed, cause the timing/sync to be thrown off more and more with increasing throttle? Hope you understand what I'm saying here.

 

[DDAADDYY]

Re: Retarded Timing

Hello again, just got back from work and am rebuilding my powerhead again but that locating pin, although it has bearing mount and is solid as a rock, still makes the reed and bearing wiggle a bit. I'm thinking of putting some on the reed so when I torque the other half of crankcase down it'll lock up. Will I have trouble removing the two halves next time or is it locked in forever?<br />Thanks

 

[DDAADDYY]

Re: Retarded Timing

Well it's all back together, 22 degrees btdc at max advance 4 at idle in gear. Goin' holidayin'<br />still squeaking a bit, but it's much better. Should be good to go. Thanks for all the tips<br />Russ

 

[DDAADDYY]

Re: Retarded Timing

Hello me again, thanks Ed for all your tips and would appreciate a line from whoohooit'saboat if he can. Well I killed it again, big time, locating pin broke free, reed block loosened to where reed stop hit crank, broke fell into back side of #3, reed broke also, much damage. Luckily for me it happened 1 hours drive from possibly the best stocked used parts guy in BC.<br />Got the new piston and reed assembly. Cylinders and bearings fine. Noticed the old one was sloppy fit so did new one with aneorobic?? gasket goo to seal the chatters on cover left from old reed cage scrubbing off the aluminum. got good compression again 125 on all three, Still workin on proper timing but buddy's going to look into that. whoohoo, did you have to advance your dist. pulley like I did?? Now there's a knock apparently from #1 with the screwdriver stethascope method of listening and a little water from #3. Gooped the exaust plate real good this time, no poppet or thermostat!!. Is that O.K.? Thanks guys, this is powerhead rip #4, am learning lots but really want to go more than 20 miles this time before ripping powerhead again

 

[jfholijr]

Re: Retarded Timing

No, I determined that the distributer and flywheel were synced when I double checked the flywheel mark and top dead center were insync. My idle speed is good just my motor is a rough idler. Any speed above the idle ciruit and she smooths out real nice.

 

[DDAADDYY]

Re: Retarded Timing

Well the motor didn't blow this time thank goodness still got the knock, just basically trolled with the odd burst of WOT goes like stink just a little trouble gettin' there. Thanks for the reply whoohoo, can you do me a big favor please. The next time you go play with your boat, can you check the Neutral Idle spark advance? Mine seems to be around 8 degrees ATDC.<br />I'm curious as maybe this thing is OK and I'm whacked. Once I align "BELT ALIGNMENT MARK" on flywheel the #1 TDC seems off but it could be me.<br />I'm guessing this as I still have trouble bootin' it and am starting to think the timing is the culprit and may be too advanced across all throttle. Don't want to blow er up again. Need to rip powerhead again to find knock but don't want to because she's blowed up just to fix knock<br />Thanks<br />Russ

 

[DDAADDYY]

Re: Retarded Timing

Hello?? anyone there??

 

[jfholijr]

Re: Retarded Timing

Sorry, been busy, I checked mine not too long ago and seems that mine was between 0 and 2 degrees btdc at idle. I'll check again soon and let ya know.