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90 AMP Fuse needed on my Starter?


jyoungs's Avatar
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Join Date: Jul 2011
Posts: 2
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07-08-11, 02:04 PM   #1  
90 AMP Fuse needed on my Starter?

I have a 99' Caravelle Interceptor that i recently purchased with a 5.0L non EFI. I have been studying the service manual wiring diagram to t-shoot an intermittent starting issue. I'm having concerns whether a 90amp inline fuse is needed on my positive starter post to terminate the battery connection? The service manual has all the variations (MCM 5.0L, 5.0L EFI, 5.7 EFI, etc. etc.) Mine (i believe) is the MCM 5.0L - non fuel-injected. While the wiring diagram appears to show an inline fuse, it's not depicted in the legend, where on the other motors it is.

I put a new starter in since i purchased but don't believe the previous starter had said fuse either.

Is it needed? This is the part in question: Fuse Assy-90 Amp, Mercury - Mercruiser 88-79023A91 from Wholesale Marine

 
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Rick Johnston's Avatar
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07-09-11, 07:37 AM   #2  
Welcome to the forums. The first thing you should do is verify which engine you have. The best way to do that is to check the serial number at this site.

After you've entered the info, click the serial number range on the results page and select "Starter Motor". If the fuse is required it will show it connected to the battery post on the solenoid. (I can't imagine why a previous owner would remove it and not replace it, but who knows?)

So ... when you turn the key does it sometimes take several turns for the starter to turn on? The most common cause I've seen is inside the starter solenoid. Fortunately that solenoid is serviceable. Remove the solenoid, taking photos or making notes every step of the way as you disassemble it. Inside the solenoid opposite the battery post is a spring-loaded contact that looks like a large flat washer. Clean that and the back of the battery post with fine-grit sandpaper to remove the carbon. You'll be amazed to find pure copper hiding under the carbon.

Some models also have a helper solenoid that can fail. Unlike the starter solenoid, it is not serviceable. You can jump its contacts to see if it's the culprit.

The ignition switch itself is also a fail point, but it's less common.

 
jyoungs's Avatar
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07-10-11, 07:35 AM   #3  
I did confirm its the MCM 5.0L. The starter is brand new as i replaced it already. The issue is intermittent and will "click" if it doesn't engage the starter. I had suspected the starter slave solenoid mounted on the intake manifold as the culprit. I had planned to bench test it with my ohmmeter. I have already polished all contacts with sandpaper to ensure good connections from the battery to starter.

 
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