advance timing question

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rsimmons42

Petty Officer 2nd Class
Joined
Aug 25, 2008
Messages
194
First and foremost, I do have the original service manual for the engine. Does not cover this. So please answer...

I have a 1977 70 hp model 70EL77s

I took the boat down to the water and backed the boat down into the water and left it tied down to the truck. I set the lower end timing and the set the idle.

Here is the setting of the advance.

Stuck the motor into gear and gave it WOT and set the advance to the spec. of 17 deg.

HERE IS THE PROBLEM. with all of the load the motor will only go up to 3500rpm. but the timing base is moving forward to a stoping point and now is set to the above mentioned.

Here is the Question. Is it normal for the boat tied down to the trailer to not go all the way to 5000rpm, due to the increased load.

AND THE COMPRESSION IS GOOD. I have all new ignition system, hince the reason for the tuning.

Please advise.
 
R

rusirius

Petty Officer 2nd Class
Joined
Mar 17, 2009
Messages
109
Re: advance timing question

I'm sure someone more knowledgable will chime in, but my GUESS is that it's not going to hit max RPM because as you suggested it'll have much more load than when planing across the water...

On the other hand, I wouldn't think it would be THAT much of a difference...

There's a "trick" you can do to set timing without blasting across the water hanging over the transom... ;) Pull the plugs, open the throttle to full and use the starter to turn it over.... Only thing is, set the timing 4 degrees LOWER than the recommended... Once it's actually running the timing will jump by 4 degrees, so if you set it "right" it would be 4 degrees higher which could spell trouble...

If RPM's are still low once in water, check your prop and make sure it's matched to the motor...
 
R

rsimmons42

Petty Officer 2nd Class
Joined
Aug 25, 2008
Messages
194
Re: advance timing question

thanks rusirius for the responce,

seems no one else knows anything about this, or is not willing to share the information. I will take it out on the water and test the boat while it is under way.

Thanks again.
 
F

Fl_Richard

Lieutenant
Joined
Jan 21, 2005
Messages
1,428
Re: advance timing question

Boat engine timing is mechanical as opposed to vaccume (or computer) advance on an auto. The important thing is it's set at WOT on the throttle it's doesnt matter if the engine is actually at WOT RPMs. The important part is the throttle it WOT.

The set at cranking speed thing works too. But I prefer the engine running method then you know it's correct.
 
C

CED8ED

Seaman Apprentice
Joined
Feb 16, 2009
Messages
45
Re: advance timing question

rusirius said:
I'm sure someone more knowledgable will chime in, but my GUESS is that it's not going to hit max RPM because as you suggested it'll have much more load than when planing across the water...

On the other hand, I wouldn't think it would be THAT much of a difference...

There's a "trick" you can do to set timing without blasting across the water hanging over the transom... ;) Pull the plugs, open the throttle to full and use the starter to turn it over.... Only thing is, set the timing 4 degrees LOWER than the recommended... Once it's actually running the timing will jump by 4 degrees, so if you set it "right" it would be 4 degrees higher which could spell trouble...

If RPM's are still low once in water, check your prop and make sure it's matched to the motor...
Click to expand...


Won't cranking your engine over like that damage your ignition system???
 
F

Fl_Richard

Lieutenant
Joined
Jan 21, 2005
Messages
1,428
Re: advance timing question

Cant speak for whether un-grounded plugs would harm the ignition. I wouldn't think so, to be safe you could use alligator clips to ground them. I don't pull my plugs, just the wires. They usually arc to ground. Never had a problem yet.

CDI says to connect all plugs to a spark gap tester, I think alligator clips clipped to the ends of the spark plug boot would suffice, that way the spark still jumps and is not shorted. Never bothered myself. You only crank it a few seconds for Idle and WOT settings.

I'd think with the plugs removed there is a good possibility of fuel+air+spark = Flame


Anyone????
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: advance timing question

You may have better luck setting the timing while on the trailer if you don't back the boat down the ramp so far. I just get it deep enough so that the water just covers the water intakes on the sides of the lower unit.
 
Sandhammaren05

Sandhammaren05

Banned
Joined
Jul 30, 2008
Messages
172
Re: advance timing question

First, you need a gauge to locate and mark TDC-don't assume that the market is set correctly! Second, disconnect all three carbs, back boat into water and set timing under load (in gear) at full throttle, about 3000 RPM.




rsimmons42 said:
First and foremost, I do have the original service manual for the engine. Does not cover this. So please answer...

I have a 1977 70 hp model 70EL77s

I took the boat down to the water and backed the boat down into the water and left it tied down to the truck. I set the lower end timing and the set the idle.

Here is the setting of the advance.

Stuck the motor into gear and gave it WOT and set the advance to the spec. of 17 deg.

HERE IS THE PROBLEM. with all of the load the motor will only go up to 3500rpm. but the timing base is moving forward to a stoping point and now is set to the above mentioned.

Here is the Question. Is it normal for the boat tied down to the trailer to not go all the way to 5000rpm, due to the increased load.

AND THE COMPRESSION IS GOOD. I have all new ignition system, hince the reason for the tuning.

Please advise.
Click to expand...
 
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