automotive coil o.k.

[Si Rey]

I replaced my ign coil with an automotive one. My tack now reads 1000 rpm high. The new coil says that it requires a resistor but none was supplied nor did the supplier know which to supply. 5.7L Merc Alpha 1 outdrive. Can I/should I use an automotive coil or bite the bullit and buy a marine coil? If I can use this coil how do I go about getting the proper resistor?
Thank you in advance for any help!

 

[Coors]

Re: automotive coil o.k.

I replaced my ign coil with an automotive one. My tack now reads 1000 rpm high. The new coil says that it requires a resistor but none was supplied nor did the supplier know which to supply. 5.7L Merc Alpha 1 outdrive. Can I/should I use an automotive coil or bite the bullit and buy a marine coil? If I can use this coil how do I go about getting the proper resistor?
Thank you in advance for any help!

Did your old coil say on it; internal resistor?

 

[Si Rey]

Re: automotive coil o.k.

My old one is a Mercury Thunderbolt coil. It doesn't say if it has an internal resistor. The reason for replacement is beacuse the old one was reading 10.8 meg ohms and the bible says that 7.8-8.8 is permissable, anything beyond that should be replaced. The tack reads 1700 rpms at idle, the engine sounds like 700 rpms.

 

[Don S]

Re: automotive coil o.k.

The reason for replacement is beacuse the old one was reading 10.8 meg ohms and the bible says that 7.8-8.8 is permissable

What is this "Bible" that you are refering to?????
The reason I ask, is the OEM service manual for an 89 5.7 with TB4 ignition says the secondary resistance should be between 9,400 to 11,700 Ohms, (Not Meg Ohms)
What was the reason for testing the coil to begin with, was it running bad or were you just futzing?
It's an electronic ignition, you need the proper coil.

 

[Si Rey]

Re: automotive coil o.k.

The bible is Cylmer, which says 7,800-8,880 ohms and mine reads 10,800. The issue I'm having is my wot rpms will fluctuate anywheres from 200-600 rpms. I could have 3900 rpms @ wot, shut down the engine for 15-20 min after fishing/swimming/sleeping then start up again and get 4600 rpms. I haven't touched/adjusted anything in the meantime. I'll shut the engine off for about 1-2 hours, eat dinner and go for a spin and rpms will go back down to 3800-3900. I recently went from a 14.5x17 aluminum prop to a 15x15 SS to increase rpms. I was successful in doing this however the rpms went to 47-4800, soooo I proped back up to a 14x17 SS. After this the rpms came down a little but still too high as I can easily redline the engine. After running this 14x17 SS prop this weekend is when I was getting fluctuations in the rpms. That is why I started looking at spark. The rpms are really changing and not the tack going array as I can hear the difference.

 

[Don S]

Re: automotive coil o.k.

The bible is Cylmer,

That's no Bible, it's a way for the people at Clymers to take money out of your pocket an put it in theirs.
That is just one more part that is just flat out WRONG.
Clymers is an AFTERMARKET manual, they try to copy little pieces of the OEM manuals and sell it to people.

Your real problem sounds like a fuel problem, not spark.

 

[Coors]

Re: automotive coil o.k.

The bible is Cylmer, which says 7,800-8,880 ohms and mine reads 10,800. The issue I'm having is my wot rpms will fluctuate anywheres from 200-600 rpms. I could have 3900 rpms @ wot, shut down the engine for 15-20 min after fishing/swimming/sleeping then start up again and get 4600 rpms. I haven't touched/adjusted anything in the meantime. I'll shut the engine off for about 1-2 hours, eat dinner and go for a spin and rpms will go back down to 3800-3900. I recently went from a 14.5x17 aluminum prop to a 15x15 SS to increase rpms. I was successful in doing this however the rpms went to 47-4800, soooo I proped back up to a 14x17 SS. After this the rpms came down a little but still too high as I can easily redline the engine. After running this 14x17 SS prop this weekend is when I was getting fluctuations in the rpms. That is why I started looking at spark. The rpms are really changing and not the tack going array as I can hear the difference.

A Clymer Bible; you need to talk to Bondo, as the owner (Kevin), is his buddy.

 

[Si Rey]

Re: automotive coil o.k.

being new to boating the only thing I see at the marine shops is clymer, what is recommended and where do I find it?

 

[Don S]

Re: automotive coil o.k.

You need the Mercruiser service manual. But here is the problem. I found you had an 89 in another post, but that is probably the year of the BOAT, and not necessarily the engine and drive.
You need to get the Mercruiser SN. there is a tag just above the aft part of the starter. What is it.
Will be a something like this, only the letter will change along with the numbers after the letter.
0B1234567

 

[Si Rey]

Re: automotive coil o.k.

Here's what I found Mercruiser 0520620. Do you have any feelings on direction for my issue? B.T.W. advice that you have given me in the past with previous problems has been right on! Thank you!

 

[Don S]

Re: automotive coil o.k.

That's not the number, unless there is supposed to be a B between the 0 and 5.......... but then you would have a 87 Wellcraft....... Doubt that by your screen name.

 

[Si Rey]

Re: automotive coil o.k.

Very funny on the screen name. No, I have an 89 Sea ray 220DA and that was the number on a metal tag just aft of the starter. reviewing the owners manual it say 0C520620.

 

[RubberFrog]

Re: automotive coil o.k.

The bible is Clymer.

We're all going to have a good laugh for a while.

Did you throw away the old coil?

 

[Coors]

Re: automotive coil o.k.

Sorry, but we can't help ourselves.
The Clymer is a piece of crap.
Get a factory manual, and life will be better.

 

[Si Rey]

Re: automotive coil o.k.

To answer rubberfrog- no I still have the old one and re-installed it. Was there something I could do with it? Ah let me re-phrase that, why do you ask if I still have the old one?

 

[Don S]

Re: automotive coil o.k.

Ok, that serial number means something, you do actually have an 89 model engine. (although it was manufactured in November 88) all the Merc stuff is 89, and that is what counts.
What you need is Mercruiser service manual #15 (Merc PN 90-816463) which covers your engine. For your outdrive, transom shield, and trim systems, you need manual #6. Good news, it's free and online to download. Go to the link below and scroll to the last page (the outline) and click on the LETTER of the section you want to look at (or save to your computer)
http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

 

[Si Rey]

Re: automotive coil o.k.

O.K. Don, Got the #15 info for engine and the #6 for the outdrive. I'll order the #15 manual from Iboats. Thank you for the info and direction. Do you have a feel on what I should be looking for in the fuel system dept? Throttle linkage/cable have full travel, the carb is a Rochester Quadrajet.

 

[Don S]

Re: automotive coil o.k.

Not sure iboats sells the oem Merc manuals, but your local dealer should be able to help you out.

Here is what I would do first to check the fuel system. Since it only happens after running for awhile, set up the gauges on the engine and go for a ride. When it starts going bad check the gauges and see what you have.

http://forums.iboats.com/showthread.php?t=167561

 

[Si Rey]

Re: automotive coil o.k.

Wonderful info and thought process, I'll look at the link and go from there. I report back with my findings so as to help other fellow boaters. Thanks again!!!!!

 

[Si Rey]

Re: automotive coil o.k.

Found a loose fitting at the fuel tank, pulled pickup tube found no debris. There is a backflow fitting at the fuel tank which I also found would leak down so it will also get replaced. Saw a fuel spot in the engine compartment right under the fuel pump. Removed fuel pump and found it was all wet right at the diaphram -eurika! I think I found a fuel leak or rather an air leak. Will replace fuel pump and related hoses and anti-siphon fitting then take on a test run. Wish me luck!