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318 tune up parts

Zminat

New member
Hi Folks,
New Forum member. First time posting.
I have a 1989 boat with twin Chrysler LM318B engines. All of the replacement parts manuals list these engines up to 1988. I have not yet seen anything posted for 1989 Chrysler marine 318 engine ignition parts for tune up. I can only assume that the parts listed for 1988 will fit my engine?
Also, My engine has Champion RN9YC spark plugs. The manual shows Champion RN12YC. Does anyone know the difference?
 
Highly likely that your engines were made long before the hull was started.....that's why most every marine engine builder uses the serial number to ID the engine and its parts. I think you will find the '88 parts suitable.

the champion plug 'numbers' are the heat range of the plug and, for those, the '12s' are hotter than the '9s'.....unless there's an issue with the engine, I'd suggest using the '12s'....
 
Highly likely that your engines were made long before the hull was started.....that's why most every marine engine builder uses the serial number to ID the engine and its parts. I think you will find the '88 parts suitable.

the champion plug 'numbers' are the heat range of the plug and, for those, the '12s' are hotter than the '9s'.....unless there's an issue with the engine, I'd suggest using the '12s'....


Makomark,
Thank You for the info.
I hope to learn lots more about my engines from this Forum.
Best Wishes,
Tom
 
Hi Folks,
New Forum member. First time posting.
I have a 1989 boat with twin Chrysler LM318B engines. All of the replacement parts manuals list these engines up to 1988. I have not yet seen anything posted for 1989 Chrysler marine 318 engine ignition parts for tune up. I can only assume that the parts listed for 1988 will fit my engine?
Also, My engine has Champion RN9YC spark plugs. The manual shows Champion RN12YC. Does anyone know the difference?

FWIW the Chrysler '85-'86 Chrysler Marine Start Up Manual calls for RN9Y for the LM318 and LM360. The hotter "12" plug should be just fine though.
In the automotive world it was common to run hotter plugs for cylinders that had fouling issues.
 
FWIW the Chrysler '85-'86 Chrysler Marine Start Up Manual calls for RN9Y for the LM318 and LM360. The hotter "12" plug should be just fine though.
In the automotive world it was common to run hotter plugs for cylinders that had fouling issues.

Hi "Daves69",
Thank your for the information.
It is comforting to know that the RN9 plug was a recommended plug in a manual. I will buy the same plug number that I am taking out since it was not an issue in the past for my engines. I have had the boat for 6 years and it ran fine. I am only giving it a tune up as a preventative maintenance issue. I do not know when it was tuned up last from the previous owner so I will now have a base line of tune up history.
Best Wishes,
Tom
 
Tom, one aspect of a "tune-up" is the ignition advance. Not just BASE or Initial advance, but the correct Progressive advance and the Total advance at the Full In RPM.
BASE is BASE all day long.... we fire up on BASE, and we idle on BASE...... and that's it.

The more important aspect of ignition advance is what occurs once above idle RPM up the power producing RPM range.
This is referred to as the Progressive and Total advance, and in most cases can be found in the form of an OEM ignition advance curve graph.

Unfortunately, no one here has been able to find anything other than BASE or Initial advance data. We have exhausted efforts.
We can find Ford and GM Marine engine ignition curve graphs.... but not for Chrysler Marine.

Point being..... your ignition distributors are old, and most likely the advancing mechanisms are worn.
If the flyweight return springs are compromised, the advance may come on too early, of which will cause engine damage.


Suggestion:

Find true TDC for #1 cylinder.
Mark off your harmonic balancer up to approx 35 degrees BTDC.
Strobe your timing marks as RPM is increased.
Using graph paper, plot your findings out in increments of 250 RPM up to 3,500 RPM or so.

Your engine should see a a fairly linear progressive advance, and of no more than 28*/ 29* @ 3,000 RPM.
This will be very UNLIKE the automotive ignition advance curve!


Here is what a GM Marine ignition curve looks like. A Chrysler Marine ignition curve will be similar.

NOTE: BASE advance is not included in the vertical scale! Vertical scale shows distributor advance ONLY.
 

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Tom, one aspect of a "tune-up" is the ignition advance. Not just BASE or Initial advance, but the correct Progressive advance and the Total advance at the Full In RPM.
BASE is BASE all day long.... we fire up on BASE, and we idle on BASE...... and that's it.

The more important aspect of ignition advance is what occurs once above idle RPM up the power producing RPM range.
This is referred to as the Progressive and Total advance, and in most cases can be found in the form of an OEM ignition advance curve graph.

Unfortunately, no one here has been able to find anything other than BASE or Initial advance data. We have exhausted efforts.
We can find Ford and GM Marine engine ignition curve graphs.... but not for Chrysler Marine.

Point being..... your ignition distributors are old, and most likely the advancing mechanisms are worn.
If the flyweight return springs are compromised, the advance may come on too early, of which will cause engine damage.


Suggestion:

Find true TDC for #1 cylinder.
Mark off your harmonic balancer up to approx 35 degrees BTDC.
Strobe your timing marks as RPM is increased.
Using graph paper, plot your findings out in increments of 250 RPM up to 3,500 RPM or so.

Your engine should see a a fairly linear progressive advance, and of no more than 28*/ 29* @ 3,000 RPM.
This will be very UNLIKE the automotive ignition advance curve!


Here is what a GM Marine ignition curve looks like. A Chrysler Marine ignition curve will be similar.

NOTE: BASE advance is not included in the vertical scale! Vertical scale shows distributor advance ONLY.

Ricardo,
Thank You for the information.
Best Wishes,
Tom
 
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