Strange starter problem

cnball

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Jan 31, 2008
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A friend asked me to help him fix his boat. Its a Stingray with a Mercruiser 383 Magnum. The engine has only been in about a year and only has about 10 hours on it. First starter went out pretty quickly and was replaced by a rebuilt unit. It stopped working after the boat sat up for a few months. When I tried to start the boat, only the master starter solenoid on top of the engine would click. I felt like it was a loose or corroded wire connection. I removed, cleaned and tighten all battery cables at the battery and where they connected to the engine block and starter. No change. I jumped across the master solenoid and nothing happened, not even a slight spark. Jumped from the large terminal on the starter to the small terminal. Nothing. Convinced myself to remove the starter at that point. With the starter out, I used some jumper cables and jumper wires to test the starter. It would turn, but the bendix would not throw out.
I left and returned the next day with a new starter. Installed it correctly. Same problem. Master solenoid clicks only. Here is where it gets really weird. Through jumping around with a screwdriver or jumper wires I found that I can get the starter to crank only if I jump with a screw driver from the large cable connection to the small wire connection. Normal except it will only work if the small wire from the master solenoid is disconnected. If the small wire is connected, nothing happens, not even a small spark.
I got out the meter and verified I have power to the small terminal on the starter when key is turned to crank position. I checked the master solenoid and even though it checked out, I replaced it anyway. No change. I'm pulling my hair out. Has anyone out there run into this before?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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welcome aboard,

your slave solenoid/relay is most likely the problem
 

alldodge

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Howdy

You cleaned the battery terminals but did you remove and clean the ground terminal attached to the block?

Next there should be a 90 amp fuse attached to the starter main terminal then the battery cable, is it corroded or damaged/blown?

Lastly, what engine and year are you working on?
 

Stumpalump

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Do the above then smack the starter with a hammer. I'm wondering if the bendix is jamming against the flywheel. The shims are long gone I bet. Read you meter while trying to crank it.
 

cnball

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Thanks for the ideas.The slave solenoid on the starter has been eliminated as the problem by jumping from the large terminal to the small terminal (engine cranks, but only when the small wire is removed). The engine ground was removed and cleaned. I also attached a jumper cable from the engine ground to the battery negative terminal. Ground is also eliminated since the engine cranks with the jumping of the screw driver.I cleaned and tested the fuse on the main terminal. I also added a jumper cable to bypass it. No start.The starter is brand new. I know that doesn't necessarily mean it is ok. Its not jammng against the flywheel, Only the master relay is clicking, not the slave on the starter.
I'm stumped for now. It is violating the rules of 12 volt electrics. It should be cranking. I'll keep trying and let everyone know what it is when I figure it out.
 

cnball

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And it is a 1 year old Mercruiser MPI 383. Don't have the serial number.
 

alldodge

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And it is a 1 year old Mercruiser MPI 383. Don't have the serial number.

Only way to get a 383 is to bore a 350 and put a 400 crank in it, or take a brand new 377 (Mercruiser 350 with 400 crank) and bore it. I'm going to say that, until you tell me otherwise that you have a 2014 or 2015 377 MPI.

That said, there is a slave solenoid and a starter solenoid, the slave solenoid is mounted on top the motor near the ECM. When key is turned to start the power goes from the key to the slave solenoid, the slave is energized and it sends power to the starter solenoid. The pic below is a typical setup, it's not yours but the wiring connection in the start circuit is the same.

Merc Elect fuel pump wiring.jpg
 

cnball

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The boat is now cranking. While I was checking things with a meter and jumping around parts, the main fuse attached to the starter terminal went out. I attached a jumper cable from it straight to the battery to eliminate it. Engine still did not crank. I went home again still puzzled. The next day I returned with a new fuse and installed it. Engine cranks. Why it did not crank with the jumper cable attached, I can't explain. Oh well, I'm not looking a gift horse in the mouth. Thanks for the ideas and advise.
ALLDODGE, I looked into the 383 a little more. It is actually an engine package available from the Mercruiser reman division. So, as we both know, a 350 bored .030" over with a 400 crank. I was wondering why Mercrusier would bore a brand new block or were they simply calling it a 383 because so many people are familiar with it. Here's a pic of the engine cover.
 

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alldodge

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Looks like you have a remanufactured 350 by Mercruiser .
image_236613.jpg

The standard 350 has a 4.000 bore x 3.48 stroke. If the block is bored .030 and increase the stroke (3.75) you get a 383. The image below I got from Merc site
https://www.mercurymarine.com/en/us...emanufacturing/plus-series-bravo-sterndrives/

Merc bored the block and installed a different crank shaft

383 stroker.jpg
As for why it didn't start, look at the starter image in post 7, it doesn't really illustrate it correctly, but the other wires coming off the main starter bolt are actually coming off the fuse. With the fuse being blown it was not supplying power to main power.

Glad to hear you get her fixed, have a great boating day
 
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