power drop under load mercruiser 3.0

[Sashap]

ok, latest update...
The other day, while I was waiting for parts I tried starting it. no spark at all. So I tried the timing light and saw nothing no matter where I put it. gave up in frustration. Then the next day tried the timing light and lo and behold there was spark. I changed nothing! But the timing was so out of whack after I replaced the distributor components (EST) all but the module and the distributor body that I figured I must have put it in 180 degrees backwards. It just sputtered, no start but did have spark. Switched it over 180 degrees then just left it.
So, today I put in a new module. At this point, I have a new dist cap, new rotor, new pickup coil, new module. And guess what? no spark...nothing, Only thing left is the fricking coil. I did the recommended Ohmmeter tests and it seems to test ok. I get .7ohms where it says .4 but a mechanic says anything under 1 is ok.
Help! I am so lost...
It's going to warm up weather wise and I would love to try the boat out as I have never had it over about 10mph due to this whole episode.
What do I do to thoroughly go over everything to verify spark? What would cause this on again, off again spark?
I don't mind putting in a coil, it's just that I half doubt it would be that after everything else I have tried. It seems ever since I took out the old dead tach that this no spark thing started happening. Something to do with the safety lanyard? How do I check that?

 

[Sashap]

put on the new coil just now and voila! spark. However, still no start. Actually, the spark could be because I reconnected the shift interrupt to the normal position from the bypassed mode. Either way, I have spark. Bought a $25 automotive coil (only thing different is that it is not coated in epoxy but over $100 cheaper).
Anyway, still no start.. So I thought I put the distributor in backwards. I turned it and it coughed through the carb so I am pretty sure it is backwards now! Which makes me ask why it never starts. The carb is approximately turned where it was before and I cannot see the timing marks with the timing light. What now?

 

[searay3]

If you had the distributor out and are not sure, it's not hard to check. Pull #1 plug. Hold your finger over the hole and turn the engine until you feel air coming out. Thats the compression stroke. Once you feel air, rotate the engine until the timing marks on the harmonic balancer line up. Re stab the distributor so the rotor points at the #1 plug wire tower.

 

[Sashap]

Followed that. Set timing starts easy but does not advance more than 1-3 degrees at 2700 rpm. Could this cause low power under load

 

[Sashap]

Did you have the engine running before attempting to put the EST into base timing mode?

If you jumpered the shift interrupt switch wires with the engine off, it probably (???) won't start. I've never tried it, but that's the purpose of the shift interrupt switch, to kill the ignition (momentarily while shifting out of gear).

1- start and warm engine
2- jumper white wires on the distriburtor
3- connect shift interrupt switch wires (now the engine should be running poorly - because the EST is in base timing mode)

But if I disconnect either shift interrupt wires or connect white tach wires jumper the engine stalls immediately. So how can I do this with engine running?

 

[Sashap]

I figured out the disconnect process but still only advanced 2 degrees at 2500rpm

 

[TurtleTamer]

It only advanced 2* after you took it back out of base mode? Sounds like a faulty ICM.

 

[achris]

... but does not advance more than 1-3 degrees at 2700 rpm. Could this cause low power under load

Absolutely... Lack of power under load will result form a retarded (not advancing ) spark....

Here's your advance chart...




Another possible cause of lack, or poor advance is a bad ground on the distributor. Find, or make, a lead to go directly from the distributor body to a good engine ground, and check the module wiring is good, especially the grounds.

Chris........

 

[Sashap]

Absolutely... Lack of power under load will result form a retarded (not advancing ) spark....

Ok but how does this help? And yes I did disconnect wires in correct order. Plus I tried two different modules. On trailer with muffs it did advance but not in lake.

 

[achris]

Sorry, I added a comment (to my previous post) that might be worth investigating...

 

[Sashap]

Good idea. Will try this tomorrow. Also, why is white/green wire voltage .9 volts when connected through the shift interrupt switch? But when switch bypassed the voltage is correct at 12 v. The purple wire is always 12 v.

 

[Sashap]

Good idea. Will try. Why is white/green wire voltage 0.9v when connected through shift interrupt switch? Otherwise both wires 12 v when joined together.

 

[fishrdan]

I did disconnect wires in correct order. Plus I tried two different modules. On trailer with muffs it did advance but not in lake.

So you got it timed to 1* BTDC in base timing mode? Did the timing advance to 12*+- when out of base timing mode? How are you seeing the timing advance, and idle timing 12*+-? Do you have an advance timing light? I picked one up at Harbor Freight pretty cheap, seems to work well.

You said the timing advances properly on the trailer/muffs, but doesn't advance properly on the water? Shouldn't do that, unless timing shunt is left in place (on the water) as achris pointed out. When you're swapping modules, are you using fresh/new heatsink compound under the module? If no compound, the module could be overheating (no advance = limp mode? I'm not sure).

 

[Sashap]

I have a timing light. Yes am using white compound on both modules. Shunt was removed before I went on water. After I confirmed advance was good.

 

[Sashap]

I’m now reduced to sitting in my boat in my yard mounting brackets, installing speakers and cleaning. Totally at a loss as to what to do. I don’t want to buy another module even though I found them at $70 because I can’t confirm if that is the issue. Would be nplugging every sensor, gauge etc be worth trying?

 

[Bondo]

I have a timing light. Yes am using white compound on both modules. Shunt was removed before I went on water. After I confirmed advance was good.

So how do you know the timin' is not advancin', on the water,..??
Did ya bring the timin' light on the cruise,..??

Readin' yer 1st post, it sounds like the carb is junk, runnin' over-rich down low, 'n starvin' the motor of gas when hammer down,......

 

[Sashap]

So how do you know the timin' is not advancin', on the water,..??
Did ya bring the timin' light on the cruise,..??

Readin' yer 1st post, it sounds like the carb is junk, runnin' over-rich down low, 'n starvin' the motor of gas when hammer down,......

yes, I brought the timing light. it just stays at 1degree.

The carb was in pretty bad shape when I started. It has all new gaskets and all ports were cleaned and tested with air flow and pumped fuel with a hand pump. Float is adjusted etc. I also poured fuel in the barrels but it just bogged down bad (too much poured in), so I poured less and it still bogged down. I also poured fuel in the bowl overflow in case the bowl was starved but no positive effect. I know it even sounds like it was bogged down due to low fuel, but pouring more in clearly didn't help even the tiniest bit.

I got yet another ignition module today (and the guy at the shop said I could bring it back to try another if this one had no effect because they sometimes are bad from the start).
I read somewhere last night that the module could go bad if the 12 volts is left on too long. This could be a thing because I clearly left it on or at least did the wrong sequence a few times. I am going to follow it to the letter and see what happens. I've got nothing else left to try. Totally at a loss.

 

[Sashap]

Well, it was the module after all. The third one I put in worked. Didn't even touch the timing when I tested it. Put in the new module and it started on half a crank. Not sure if I got lucky on the starting because I just came back from the lake after re-timing it to 1 degree BTDC and it takes a few turns to get it going. I think it's just the gas/carb that I need to learn how to start it without using too many turns of the engine.

Regardless, it started and even planed up (albeit a little slow at first because it was cold). I got 3500 RPM and 33mph on the old speedometer. I did use GPS and it showed about that. I know I have to change the gimbal (it growls even after lubing, so I ordered one).

Thanks all!
I will open a new thread regarding performance issue.