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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10972
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I started the season with issues - engine wouldn't crank.

Customer Question

I started the season with issues - engine wouldn't crank. Replaced battery, starter solenoid, starter fuse, and starter. Boat ran great all season. Last weekend boat was fine and drove to beach. Back of boat hit with fairly big wave from passing boat. Then went to leave... No crank. Has good chg to battery, fuel. Makes noise like blower but that's it. Has power to instruments. Now what?
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
4.3 L mercruiser V6 I/O
Expert:  Tan replied 1 year ago.


This may take more than one reply to solve the issue you have.

Do you have a volt meter so we can check voltage is getting to the starter from the key switch?

Could I get the engine serial number please?

Also check the battery cable connections on the battery when you hit the wave it could have knocked the cable loose at the battery. We also need to use nuts and lock washers on the battery cable connections getting rid of the wing nuts.

Customer: replied 1 year ago.
Unfortunately serial number sticker has fallen off engine. I have checked with voltmeter, and it is appropriate. I've checked all battery connections and they are tight. I've even tried jumping The engine without success.
Expert:  Tan replied 1 year ago.

Ok when you say you hear a sound like the blower is it the blower or is the starter making a growling sound?

I'm going to post a diagram of the start circuit for your engine. I need you to test voltage at these locations with key in the crank position not on position but crank position. Check voltage at A,B & C .

Post back with findings.

Customer: replied 1 year ago.
I tried jumping starter solenoid too... Got depth warning and blowing noise again. Not the blower itself, no crank just sounds like electrical whirl (I am unsure from where).
Expert:  Tan replied 1 year ago.

Ok whirring sound is usually low voltage bad connection or bad starter. We can eliminate the starter as it is new.

Try this check the voltage at the starter terminal A with key in the crank position. The only way we are going to find the problem is through doing voltage tests. This issue can be any number of different problems. The most likely is low voltage or cable connection. So lets start with checking the voltage at the starter. Can you do any of these tests? If not we will have to try something different which will be more complicated.

Customer: replied 1 year ago.
I can and will get back to you... Just away from boat at the minute
Expert:  Tan replied 1 year ago.

Ok great. We must determine that we are getting good voltage to the starter when the start circuit is activated. You can have a good voltage reading but it can go away when you try to crank the motor. Since hitting a wave brought this issue on I am thinking something has been knocked loose either on the engine or the battery . Your symptoms tell me loose connection or poor voltage delivery to the starter. I have done hundreds of these engine with start issues and have found every problem.

I will be here all week so post back when have done the checks. We will get you fixed.

Expert:  Tan replied 1 year ago.

Here is another test you can do if you don't have a friend to turn the key from voltage readings. At the starter with a jumper wire jump from terminal C to A while check voltage on C when cranking the engine. What is your voltage reading?

Customer: replied 1 year ago.
12.8v at battery and 0 volts at A,B,&C when ignition in cranking position
Expert:  Tan replied 1 year ago.

Ok you have a bad battery cable, connection or battery.

Check the battery cable ends and connections. Check the connections on the battery and the engine both positive and negative. Then connect the volt meter to the battery and crank engine. Does the battery voltage stay above 9.5+ volts? If yes then you have bad battery cables. Do you have a battery switch?

Customer: replied 1 year ago.
11.5 on battery w crank
Expert:  Tan replied 1 year ago.

Ok that leaves the cable or the connections. Check both. Do you have a battery switch?

Customer: replied 1 year ago.
No battery switch.Are the cables easy to replace? Why would they go bad all of a sudden? Does it matter that my instruments still get power?
Expert:  Tan replied 1 year ago.

Thta's why we need to check the connections as they could have come loose or corroded and you will loose voltage all of a sudden. Now likely that the cables themselves are bad but possible. This is an easy repair just remove the cables one at a time. Disconnect the negative from battery and engine block, clean the connections real well sand paper or wire brush reattach. See if engine will crank. If no then do the same procedure with the positive battery cable. Try to crank engine. If nothing replace the cables. Replacement is just disconnecting both battery cables replacing with new.

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