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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14299
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a mercruiser 1.7dti that we had rebuilt but now really

Customer Question

I have a mercruiser 1.7dti that we had rebuilt but now really slow cranking over
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.
Hello my name is ***** ***** am I speaking with?
Do you have a voltmeter and do you know how to take basic voltage measurments?
Customer: replied 1 year ago.
i do indeed
Customer: replied 1 year ago.
My name is ***** *****
Expert:  Jason replied 1 year ago.
Hi Graeme. Do this for me. Set the meter up on the battery. Positive lead to positive terminal. Turn the key to start. What does the voltage read? Next, move the positive meter lead to where the main battery cable connects at the starter motor. Turn key to start. What doe the voltage read? Let me know what you get for both readings.
Customer: replied 1 year ago.
ok done that and they both read the same 12.95 v the starter motor is brand new
Expert:  Jason replied 1 year ago.
Are you measuring voltages with a battery charger hooked up? Do you have a standard lead acid battery?
Customer: replied 1 year ago.
yeah the battery is new lead acid battery, no charger on
Expert:  Jason replied 1 year ago.
A brand new lead acid battery should read 12.6 volts tops... So it shouldn't be reading 12.95. Also, when measuring voltage at the starter it's normal to see a 1 volt or more drop. So you definitely should not have the same at the starter. Did you measure both voltages with the key held to start, and the engine actively cranking over?
Customer: replied 1 year ago.
I shall re check back in a sec
Expert:  Jason replied 1 year ago.
OKay
Customer: replied 1 year ago.
ok 12.74 v static battery charge, when cranking 10.66 to9.88 then to the starter motor 10.11 to 9.99
Expert:  Jason replied 1 year ago.
Voltage is acceptable. If it's spinning over slowly that would normally mean the starter is bad. However, because this engine was just rebuilt. Did the person who rebuilt it spin it over by hand to make sure nothing was binding internally? Did you rebuild this yourself, or was it done by a company?
Customer: replied 1 year ago.
actually it was rebuilt last year and was running up no problem both out and in the water, we winterized it and now have this problem, i removed the the injectors and was turning over quickly with no knocks
Expert:  Jason replied 1 year ago.
Okay good. Then at this point I would feel comfortable replacing the starter. It needs 9.5 Volts or better to spin the engine over quickly. And it definitely has enough voltage. So at this point you would replace the starter. Does that make sense?
Customer: replied 1 year ago.
it does, but it is a brand new starter
Expert:  Jason replied 1 year ago.
When you ask your questions there is a window where you are supposed to type in everything you have done on your own so far. Since you didn't fill that in, why don't you go ahead now and tell me everything you've done on your own....
Customer: replied 1 year ago.
ah sorry, I did not see that box, this is new to me, apologies OK so last year the third piston started pitting, i believe this is a common problem, so we put in new pistons, rings and turbo with the engine completely out the boat, put the engine back in and it started up fine. I run a training company but we did not need it over the winter so removed battery and put it in dry stack. this year lowered into water and put new battery in and it was really slow to turn over almost raspy in sound, so pulled it out of the water and checked it had not seized. pulled injectors and hand cranked to make sure no water in the cylinders, checked starter solenoid was faulty so renewed starter motor and solenoid then bled the fuel system. but still cranking slowly, it does have a kill chord system
Expert:  Jason replied 1 year ago.
By renewed the starter motor do you mean it was rebuilt, or was it replaced with a brand new unit?
Customer: replied 1 year ago.
brand new unit
Customer: replied 1 year ago.
and as i say it sounds raspy as it turns over
Expert:  Jason replied 1 year ago.
There is 1 more test we can do and that is a voltage drop test across the negative cable. Hook your meters positive lead to where the ground cable connects on the engine block. Hook meter negative to the battery negative post. Hold the key to start. What kind of reading do you get on the meter?
Customer: replied 1 year ago.
ok no idea if this is right but it read 0.38v
Expert:  Jason replied 1 year ago.
that would be right.... (And a good number)At this point i'm out of ideas. Will the place you bought the starter from give you another one to try?
Customer: replied 1 year ago.
I could always ask, it was shipped a distance, but i can ask
Expert:  Jason replied 1 year ago.
Is the engine trying to start when cranking it? Is it trying to start but misfiring?
Customer: replied 1 year ago.
no it is cranking but just sounds really laboured no misfire
Expert:  Jason replied 1 year ago.
It's definitely possible you got a bad starter. At this point all you can do is change it out for another one and keep your fingers crossed. That's what I would do if you had brought the boat to me.
Expert:  Jason replied 1 year ago.
Good morning, just checking in, any luck?

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