Timing light 4 stoke 2 stroke ?

[stan]

Hi
I am using a dial setting timing light on a 6 in line merc 1976
the dial reads twice what is should be, 43 Degrees BTDC
Do you divide by 2 when using these timing Lights? Had this simular problem before with another timing light.
Now again. Does this make sense or am I doing something wrong?

[gaineso]

I had the same problem when I was trying to check out my '86 inline. Finally realized that the dial read for a for a half speed distributer and I needed to divide by 2.

Verified that on # 1 and then rechecked all 6 with boat on trailer backed down the ramp. WOT, I've got it set at 17*. Haven't had time to do much running yet, due to other circumstances, but should be able to get out Wednesday. If all goes as expected, I should be set for awhile, at least the rest of the summer.

[Forkin' Crazy]

Yea, I think that is it. Mine has a switch on it to toggle from 4 stroke to 2 stroke

[Raceman]

Why don't you just set it on zero and use the stock Merc timing marks?

[stan]

Thanks for the information, I will try it again on the weekend, for setting the gauge to zero was not sure if zero is true zero for this this application thought it would depend upon the time constant in the device used. I will try both /2 and zero setting and see if they line up the same.

[gaineso]

Raceman, the stock timing marks work great for #1. When you need to check all 6 they don't work. Used JSRE TDC indicator to index TDC in all 6 and marked that. Then used dial on timing light to se where they all were.

[stan]

Thanks for the post, are you telling me there is a reason to check the timing on all 6 cyclinders? I used a dial gauge to set up TDC on number on then set pointer.

[gaineso]

I was trying to determine the reason for detonation on #4. Found out my timing was varying about 15* until I pulled the idle stabilizer off. Then it settled down.

[stan]

Mine does not have an idle stablizer, its a 1978 115 6 in line, what year is yours? Is it the same block? I am going to set the timing to 19* from 21* I notice yours is 17*, if its the same block I wonder what RPM you get and what prop you can turn. Mines seems to like a 19 pitch cupped, hard to turn the 21 cupped.

[gaineso]

Stan, mine's an '86 on an '87 Glasstream 15V Bass Boat. About 850#s empty, probably 1700+ ready with full fuel.

I'm turning a Turbo II 22" 6,000 RPM with C/L of prop shaft at 3 1/4 inch below pad. Boat has a built in 6" setback and I'm on a 6" setback T&H jackplate. Probably be better off with a little more cup and rake or maybe even a 23". Bring the R's down to 5800. Seeing 59.4 GPS as it is now with full gas (18 gals) Got new Hydraulic steering from Rickracer and when I get it on AND THOROUGHLY TESTED, I'm gonna see what I can get with about 3 gals of gas and 50#'s of trolling motor off the bow. Raceman and a few others here are real gurus on the old inlines and can help you out. They really helped me.

RUN GOOD OIL (MERC OR FULL SYNTHETIC) AND PREMIUM (92 OR 93) GAS ONLY. Ask me how I know.

[stan]

Wow good engine !

I have a hard time breaking 5,300, As for how you know Octane
Most likely the same as me, "muffed pistions?" I rebuilt my machine with low dome pistions, can't get 92 octane around here easily, the province wants to make manditory gasahol soon.

Can't be same block as mine to get those rev's it's odd mine shows to be same block as a 90 but it reeves higher than the 90's....I only had a few minutes on the weekend to check my machine out, looking forward to seeing how she runs, spent 1 hour in idle and about 30 seonds up at half trottle not sure if I am happy or sad for all the work. $2,000 into her so far 6 new pistons, crank was perfect, re-did carbs, lower bearing, distributor, water pump, Having Retro Classic 78 painted on coul shortly. Odd never got high revs out of mine, having the tach replaced this week - perhaps it was reading in error - will find out shortly... What's your opionion on the older 78 merc's I kept it as I love how she looks and it ran great for 25 years till I got stuck with crap gas that is. Was amazed to find the old six inline are getting hard to come by. For the jacking, Tried, "NO"
good, lifted it up 1 inch the back of the boat wants to be where the front is, Scarry ride, will be lowering it back down on the transom. Can't steer at all up when raised
Boat here is Glasspar G3 newer version looks cool drives scarry and odd, not much of boat, just looks cool - in real good shape so I am stuck with it

Stan

[Jeff_G]

The 90's are choked down 115. RPM is just a matter of prop, weight and balance. All the dist models should be timed at 21* or less. 19* is safer but you lose a little on acceleration. The adi models the timing is 21 but the switch boxes retard the timing around 2* at WOT. So at cranking speed you would set the timing at 23*. But if you do you MUST check the timing at WOT. Index the flywheel and check at WOT on all the cyl. don't worry about #6. Just use some fingernail polish to make the timing marks and a degree wheel. Although better you don't even need a dial indicator. A straw will work fine.
Do a search for setting timing.
Gasahol will not hurt the motor a long as you have updated all the hoses and carb needles and seats. It's not the best in the world either.
If all you can get is mid range back the timing to 19*. Only use BUHW or L76V plugs, and check your water pump impeller.

BTW I turn my 150 at 68 to 7200+rpm with a 26 or 28. :D

[gaineso]

Stan, for one thing the motors in the 70's were crankshaft rated power and my '86 is propshaft rated. That's 10 or 15 percent difference. Sounds like your boat may be a little heavy. You might even need to go to a 17" prop. 5300 is a little low on the revs. If you can't get 92 min gas, better back your timing to 17 or 18 max. BUHW's at www.sparkplugs.com were $3.10 each including shipping

[stan]

Thanks, one note I have installed "Low Dome
pistons to lower the compression. This would reduce the amount I need to reduce the timing. My problem is I don't really know by how much? I suspect your stating 17* 18* on crap gas with the stock high dome pistons? Have you had any experience with these engines that have installed the lower dome pistons

Stan

[gaineso]

My only experience with inlines is the one I have now which came with lower compression. You might want to ask Raceman about it 'cause he has a lot more experience with them.

[stan]

How does this posting work to ask Raceman ?
I see he posted here but how do I direct the low dome, timing question to him directly, Your notes on your machine have me questioning if I should not have just updated to a newer year, however if it performs like it did before I will be happy enough.

[gaineso]

You can just use Raceman as a topic or PM with a question.

[Jeff_G]

If you go with the low domes you can keep the stock timing with no problem.
If you are replacing all the pistons replace them with the newer 2 ring semi-keystone ring pistons. They come in low and high dome and are avail. from both Mercury and Sierra although the Sierra list for about $50 less. I can get you what ever you want. The Sierra pistons are just fine even for performance work, and install slightly easier (less ring breakage).

[stan]

I have installed 6 wesico low dome 2 ring pistons. The block has been bored 20 thou, it just a matter of what timing now. The motor is now low compression.

[stan]

Hope this helps others, and thank you all for posting

The timing light was divide by 2 for stroke what ever the dial read
both the dial /by 2 and the stiker read same when I dial in 0

I set it up at 17 degrees, there was no difference in speed,
I have tried 18 19 and 21 there was a little more pickup measure 0 to 30 Mph wasn't much

I returned to my 17 cupped hit 47 MPH at 5,300 RPM

Will be trying a straight 17 next weekend

Can't really turn the old 21 cupped any more,
could be the actual prop had it welded perhaps the curve
is not in spec.

Had Artist paint Retro Classic 78 on the upper cowl, 25 years of service, not bad and still a very good looking motor

Started to work on my neighbors motor's Roars like a lion his 115
80 style actual 140 hp motor, he turned 49 Mph with a 17 non cupped, found burned exhaust gasket and crack in exhust bridge block may be able to bridge weld.

Had the unit idle for 2 hours at dock breaking in, forgot how much fuel these units take idling


Thanks all

Stan