Ob starting problem

[mississipi]

I am hoping someone with electrical  experience can help. I have a 06 champion and a 115 Yamaha 4 stroke.  It requires a fully charged battery to start. If not it turns over very slow. The starting battery is a new 1000 marine cranking amp. It is mounted forward so there is about 10' of #4 wire going to a terminal box where it attaches to the engine harness. All connections have been cleaned well. Before engaging the starter there is 12.6 volts at the battery and on the starter solenoid. Engage the starter and voltage is 7.8 to 8.2 . Attaching a fully charged battery directly to the engine harness I get 9.5 to 9.6. I attached a set of heavy jumper cables directly to the starter and I get 10.0 to 10.3 volts.   I bought the boat new and all wires, etc. Were factory installed. It has always been sluggish starting but seems worse  now. Starter is drawing 150 to 160 amps. 
I am wondering if the # 4 wire is heavy enough or do I have some type of starter, solonoid issue. Any help would be greatly appreciated.

[mwardncsu]

How old is the battery? Perhaps that even while charged it just no longer has the cranking Amps to do the job. Have you tried a new battery, or had your existing one load tested.

4ga over 10’ seems light but depends on the requirements for the motor I guess - my 250 has something more like 2ga I think

[mwardncsu]

Whoops - missed the part about it being a new battery

Is it 10’ from battery to motor, or 10’ from battery to some connection panel and then further to motor

At 10’ and 160a you have a 7% voltage drop - delivering 11.2V with an ideal conductor of 4ga. If you have more like 15’ total length then you’ve got a 10% drop.

Are all connections - both on the positive and the ground, clean, tight - at the battery, the motor and anywhere along the way?

[mississipi]

10' from the battery to a terminal post. There it connects to the engine harness which is about 5'. About 15' total. There are connectors at the battery, terminal post,ground to the engine and to the the solonoid. All are super clean, clean bare metal on the engine ground. Wiring LOOKS ok, no sign of any corrosion, at least on what I can see at the terminal ends.
Assuming 10% loss, that means I should have around 11 volts when the starter is engaged? I have only about 8 when I go thru the whole 15'. I can't find exactly what the starter amp draw should be for my engine but 160 amp does sound excessive to me. Thanks Mike for your help

[steviejayvaughan]

I have the same outboard it’s a 2004 model. Does it turn over slow once it is warm? Also put a breaker bar on the flywheel nut and see if you have any mechanical resistance. What is the battery voltage once the engine is running?

[mississipi]

No mechanical resistance that I can find. Engine operates perfectly except for slow turnover on starting. Battery voltage is 13.6 to 13.8 running. Dosent seem to matter if engine is warm or cold if the battery is not fully charged it turns over slow. Thanks for trying to help

[rockchasr]

I don't know a lot about outboard engines, but, ignition timing can make an engine, hard to turn over. Just a thought....

[mississipi]

Not sure yet but I think I might have found the problem. I decided to pull on the #4 wire from the battery to the terminal post. It runs under the deck and when I pulled out all the slack the wire was 15 ft long. I have ordered 9 ft of #2 wire. That will change current path from 30 to 18 ft. I am hoping the larger wire will also help. Thanks for the suggestions

[hotdog]

Good luck. I hope that does the trick.

[mississipi]

Replaced the 16' of #4 wire with 9' of #2. I now have 10.2- 10.5 volts at the starter. Problem Solved.

[Yam]

Thanks for sharing. Great info!

I'm glad you solved it!

[31Airborne]

Learnt me something here. Nice work, dood.