Starter quickly losing power

[andy65]

The starter (Bosch) on my Johnson 70hp VRO from 1986 is quickly losing power, if the engine doesn't start during the first minute, the starter hardly manages to turn the engine around.
What can be causing this?
The battery is not the problem, I've tried with a new one.
I assume that the starter is too old and tired, and plan to buy a new one, any other suggestions?

 

[WillyBWright]

Re: Starter quickly losing power

I'll guess corrosion in a cable. Look for a swelled section. Sometimes water gets inside and the strands corrode and become separated from each other. As current passes through each individual strand, they heat up making even more resistance. Otherwise it sounds like the classic symptom of an old battery with reduced reserve capacity. You are using a Starting battery and not a Deep Cycle, right?

 

[tashasdaddy]

Re: Starter quickly losing power

Andy, remove and clean both ends of the battery cables, so that they are shiney, also the cable from the solenoid to starter. check for nicks in the cables. and make sure the connectors are on the wire good. the cable tend to corrode from the inside out, if nicked, corroded wires, and connections, heat up and cause resistance to the follow of electricity, thus the starter doesn't get enough. if this doen't solve the problem, take the starter to a starter/alternator shop for a rebuild, save lots of money over new.

WBW were at it again, typing at the same time.

 

[kenmyfam]

Re: Starter quickly losing power

If the battery is not the problem then as stated above you are getting excessive current drain and / or resistance from the cables when you are activating the starter. By pass them with a pair of good quality booster cables if you can to determine if that will solve it and if so replace the cables. May as well have the starter checked out as well for future peace of mind.

 

[BoatBuoy]

Re: Starter quickly losing power

...if the engine doesn't start during the first minute...

Man, you have more problems than the starter motor if you crank a minute before it starts. 10-15 seconds should do it.

 

[andy65]

Re: Starter quickly losing power

Man, you have more problems than the starter motor if you crank a minute before it starts. 10-15 seconds should do it.

Tell me about it... However, the engine is practically only this hard to start when it has been driving the boat at idle or very low rpm for a while and then suddenly dies. Could it be flooded?

 

[andy65]

Re: Starter quickly losing power

By pass them with a pair of good quality booster cables if you can to determine if that will solve it and if so replace the cables.

Would it be possible to run the starter engine for a couple of minutes on land without water cooling?

 

[tashasdaddy]

Re: Starter quickly losing power

go to walmart, and buy some muffs, don't jepardized the impeller. they are rubber and heat up very fast.

 

[andy65]

Re: Starter quickly losing power

I measured over the (now uncharged) battery's poles the voltage to 10.5V, and the exact same voltage right before the solenoid.
When running the starter the voltage over the battery poles decreased to 5.9V, and before the solenoidand over the starter's contacts to 3.9V.
So, 2V is lost in the cables to the starter when it's running, but when it's not there's no voltage loss in the cables.
I guess this points out that the cables are bad, but I have checked them out without any defects.
What's strange though, that I measure 1.4V over the starter's contacts when it's not running, so 1.4V is leaking through the solenoid.
If I try to measure resistance in the solenoid, however, no electricity is let through from the multimeter.
Changing the solenoid seems like a good idea, but do I need an orignal part, or will any relay tolerating the current do the job?

(I will, of course, repeat these measurements when the battery is charged.)