Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

[ntheyer]

I have the same, or so I think, issue as Freebeetony. I ended up replacing my ignition coil with an old one and it made a huge difference. I went from 3200 to 4200 RPM on my 1995 3.0 Merc. I thought that was the issue, so I just bought the entire ignition system new. Prestolite cap, rotor, points, condenser and wires. Guess what happened... I went back to the exact same symptoms. Now I am really baffled?!?!? While out on the water, I fooled with the point gap (dwell) just to experiment and found that it seemed to get better the more gap there was, but maybe I'm full of it. What else could the issue be? It really seems to be happening under load. engine speed is less of an issue. If I bury the throttle out of the hole, the 'bog' will happen. I also concur with Freebeetony that it is not exhaust or carb in my opinion. I've eliminated all of those issues. My question is how much of a factor are plugs? I have NGK BR6FS Plugs installed. The gaps are(.35) and adjusted my timing to 6 deg. Color was a nice darkish tan brown. My suspicion is that the ignition system is having a hard time making a good spark when under load. Is it harder for an ignition system to make a spark under load, or am I again, full of it!? I've been working on this for three months now. I've been following Freebeetony and we have very similar, if not the same, issues. What could be a weak point in the igniton system? Any help would be great.<br />1995 Mercruiser 3.0 with Prestolite distributor and conventional ignition.

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

It looks like the current plugs that are in are short. The problem I have is that I have the Clymer manual and it only shows the EST igniton system. This show timing should be set to 1 deg BTC. I have a Prestolite ignition. could someone please tell me what plugs I should use and what I should set the timing to. I have the dwell set to 30. Sorry for being so dumb about this. There are no stickers on my valve cover and I have never been able to find my Engine Serial number to be positive. Thanks for the help.

 

[novicetech]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

My manual only covers to 1994 but says point gap @0.016, dwell @ 39-45 degrees and timing @ 8 degrees btdc. It is a clymers as well, you might want to find some acmr43t plugs too. have you checked the fuel line for collapse when trying to run at wot? sometimes if weak it can collapse internally.

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

The fuel line is brand new. It is definitely not that because it happens right out of the hole, or at any speed. There is fuel in the carb bowl so it is not that. Fuel supply is good. I notice the MR43T plugs are normal, or short reach. Should I have those plugs, or the MR43LTS, which is the long reach? Will that make a difference? Will the long plugs fit without hitting the piston crowns? I don't want to damage anything.

 

[tommays]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

http://www.boatfix.com/merc/Servmanl/13/13covr2.pdf <br /><br />you can have a look here it covers the 3.0 motor<br /><br />but if your last repiar made it worse thats realy what you need to look at<br /><br />tommays

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

I looked up the cross reference on the plugs. It looks like the only difference is the reach of the plug. Could this make a big difference in runnability of the engine? I know it's ignition because when the dwell is extremely high, or low, I have the same symptoms, only at a much lower throttle position. It really is dependent on the 'load' on the engine.

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Thanks for the link. It pretty much is the table of contents only though. Am I missing something?

 

[Ralph 123]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

GO to the last page (the outline) move your cursor over the section letters it will turn to a finger pointing - click and it will take you to that section

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

It says that the link does not exist?

 

[Don S]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

You may have the same problem as FreeBeTony, but that is where the similarity ends. Engines aren't the same different types of ignition systems and you have been giving him advise on what to do?????<br /><br />You have been using the wrong manual, still don't have yours adjusted right by a long shot, and you wonder why it won't run...... Geeeez, I wonder.<br /><br />Set your dwell to 39° to 45° set your timing to 8° BTDC at 700 rpm (NOT 800 to 1000). Then check your advance timing and make sure you are getting 24° at 4100 rpm.<br />Once you can make yours work then give advise, but not until.

 

[FreeBeeTony]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Don......he hasn't been giving me advise, it's more like we are comparing notes.<br /><br />He/we realize the engines are different but the problems do seem very similar.<br /><br />And just like you said in another post.......it's hard to tell without actually hearing/seeing and engine run.

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

I appreciate this information. First of all, I didn't mean to me 'advising' anyone, just relaying what happened after I did something. No analysis, just information. This has always been a bit of a challenge for me, so I apologize for the dumb questions. I followed your advice Don S and have everything dialed in exactly as you have told me. Dwell is at 40.9, 8 deg BTDC at 700 RPM verified by Fluke electronic Multimeter off the coil. The one thing that I am not positive about is the timing advance. It looks like relatively low in the RPM range the timing smoothly advances to I would have to guess is the 20 degree range. I am just visually estimating based on the stamped gauge that goes up to 12 degrees. I can't be positive that it is going up all of the way to 24. I would say somewhere around 2500 RPM or so and all the way up past there, it is all the same. The timing does not really fluctuate at all until the RPMs really start coming down low. All of the advance is happening down low. I pulled the distributor plate off and looked at the weights again. They are not rubbing the distributor housing and they are free and clear when I move the weights out by hand. There is one larger gauge spring that is loose right up unitl the weights are all the way out and there is one smaller gauge spring that seems to be, well, 'springing' well. Is there anything I can do to really verify whether the advance is going all the way up? My symptoms are that basically after 3/4 throttle or so, the engine 'bogs' or just does not want to develop more power. This coincides with 3200 RPM on my engine. I had tried swapping coils and had a dramatic improvement when I went to an old coil from 1974. I consequently ordered all new ignition components and it went back to the same symptoms. Again, sorry for advising others. Just meant to let others know what happened when I did something. I really do actually appreciate everyone's help.<br /><br />Nicholas

 

[tommays]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

a timeing light with and advance dial is pretty cheep at places like auto zone<br /><br />the dial will let you set it at 24 deg which will then read on the 0 timeing mark at full advance<br /><br />tommays

 

[FreeBeeTony]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Nick, I don't think an apology is necessary......we are all working to help eachother here. At least that's how I look at it. If anyone here can relate to your frustration.........it's me!

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

I've been looking around for new springs for this distributor, but it looks like they are discontinued. Should I just eliminate all of these issues by buying a conversion kit for electronic ignition? Any thoughts? Or does someone know where I can get 24-810830?

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Timing light set me back $70.00 and the advance is spot on. Idle at 700 RPM at 8 deg and 24 degrees exactly starting around 2200 RPM. What else could be the issue?

 

[ntheyer]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Timing light set me back $70.00 and the advance is spot on. Idle at 700 RPM at 8 deg and 24 degrees exactly starting around 2200 RPM. What else could be the issue?

 

[ron7000]

Re: Replaced Complete Ignition System, Still no Luck! Same as FreeBeeTony

Originally posted by ntheyer:<br /> I looked up the cross reference on the plugs. It looks like the only difference is the reach of the plug. Could this make a big difference in runnability of the engine? I know it's ignition because when the dwell is extremely high, or low, I have the same symptoms, only at a much lower throttle position. It really is dependent on the 'load' on the engine.

You weren't entirely clear on your post.<br />Did you look up the spark plug # for your year/model engine and did it list AC-MR43LTS?<br />Or something other than MR43T?<br /><br />I have a 2002 3L engine, and it runs MR43LTS which is sometimes called long reach or extended reach. It's reach is 0.708". ACMR43T has a reach of 0.460".<br /><br />Spark plug reach depends on the cylinder head, not the ignition system. I don't know what year the cylinder heads changed to use the longer reach plugs. If you're supposed to be running 0.708" reach plugs and you're running 0.460" reach plugs, then they're barely reaching into the cylinder and not igniting the fuel properly. Yes, that will make a huge difference!<br />If you replaced a whole ignition system and the cause of it all is $8 worth of spark plugs,

<br /><br /><br />if you still have the problem, or can't verify via engine serial # the correct plug, do this:<br /><br />buy one mr43lts or ngk bpr6efs, and you are going to sacrifice the plug. I don't think you'll mind $2 at this point.<br />First, gap it at 0.050". take all plugs out of engine and rotate engine by hand so that #1 cylinder NOT at top dead center. Install 0.708" reach plug. rotate engine by hand, if piston don't hit plug then that's the one you probably should use. Next, remove plug, open gap to like 0.080", just bend electrode out so it projects further into cylinder. See if piston contacts plug when rotating by hand. If it don't, then there's definitely going to be no piston contact and most likely the plug you should be using.<br /><br />Spark plug gap is dependent on ignition system. High power (electronic) ignition systems can run larger gaps: 0.040"-0.060". Weaker ignitions (points) run smaller gaps: 0.030"-0.035" Simple as that. If you're running points ignition, it would be well worth the effort and money and better in the long run to get an electronic ignition, either a conversion or whole new distributor and coil. Hope you fix the problem.