Engine cranks slow, everything is new (post 10hr break in period)

[hubrvpete]

We rebuilt a 1979 Bayliner Trophy last year, put a new 350 and rebuilt volvo 280 outdrive. We ran it through the break in period, fixing things along the way. We just ran it again to do an oil change, and it ran out of gas. Filled the tank up, and now it won't start.

~It's getting plenty of gas in the carb, it's getting spark, but turns over slowly.
~We've got 2 new interstate deep cycle batteries, charge appears fine, but the output drops to about 8 volts when we crank it over.
~All new wiring.
~Just changed the coil, new electronic ignition module (it burnt one out??) and a new starter (again on the mechanics recommendation)

We were told that electronic ignition module may have burnt out from leaving the key on?

Kind of at a loss now.

 

[alldodge]

Howdy

You shouldn't be trying to start a motor with deep cycle batteries, you want starting bats. If the two batteries are in parallel together and your still dropping to 8V you may have a bad battery or your drive or motor is locking up.

Suggest removing the plugs, mark which wire goes where. Pull coil wire and crank it over it should spin fast.

If it does better but not good, pull the drive off with plugs out and try again

 

[alldodge]

After cranking are your cables hot?

 

[hubrvpete]

Thanks for the suggestions, I'll check into all of that. We've never had an issue with our other boats with those batteries, but it's certainly worth considering.

 

[-JR-]

Check your engine timing ,if to much it will fights it self on cranking making it hard and slow on cranking.
Are you sure you but in good fresh Gas ? Old gas will not mist and will only flood the engine.
(license mechanic for 25years)

 

[jerryjerry05]

Could be: dead cell in battery, weak or under charged, loose battery cable, bad starter(even if it's new), bad fuel??
​Remove the plugs and check for water. Then try turning it over??(Alldodge) pull upper gearcase.

 

[hubrvpete]

Just filled the tank, from empty, with premium gas. Just tested both batteries, nothing wrong with either. It was just running, so i don't think the timing would be an issue. We are swapping one deep cycle battery out for a new cranking battery today. It was also suggested that since it's a new engine, if it was flooded, it could have washed the oil from the cylinder walls, making it tougher to turn over. Remedy was to put a bit of oil down each spark plug hole?

 

[hubrvpete]

The gas in the fuel-water separator looked perfect.

 

[alldodge]

Remedy was to put a bit of oil down each spark plug hole?

No, bad idea, the gas washing the cylinder walls would wind up in the oil pan. Putting oil in the cylinders is not needed and if you put to much you could hydrolock. It would take a lot of oil, but this isn't the issue right now.

You said it was just running, and if it was running OK, then your problem may just be in your cables and corrosion.

So crank it over then fell the battery cables and the ends on the battery and starter. If their hot you have a bad cable or connection.

 

[-JR-]

Is it turning over really slow. might be just a bad starter .Is it getting hot ?
Try placing a volt meter on the battery while cranking. Don't want to see less than 9 - 10 volts on a regular battery while cranking ,not sure on a marine battery.try at the starter and see if there is a voltage drop. should be the same .
Be sure there is no black build up on the posts or inside of the clamps.check you ground cable.
Did you try pulling all the spark plugs and see if it turns over faster. Might have scored a cylinder .and it got tight when it cooled down.
Can you turn it over by hand ?
If you flooded it ,it would turn over easier because its wet .
I don't like to recommend this unless you know what you are doing .....if you can get it to turn over ,spray some starting fluid down the carb then give it a crank.
Do not crank while spaying,normally one over sprays then .just needs one quick squirt.

 

[hubrvpete]

Tried with new batteries, the wiring is all brand new, still not starting.

It seams to fire/spark as the key turns off, but no spark while turning it over now. Not sure if the ignition itself could be faulty?

Going to try another coil, even though this one is brand new.

 

[alldodge]

Tried with new batteries, the wiring is all brand new, still not starting.

It seams to fire/spark as the key turns off, but no spark while turning it over now. Not sure if the ignition itself could be faulty?

Going to try another coil, even though this one is brand new.

Being a 79 you should have points and a ballast resistor wire. Try this, turn the key ON, and run a jumper wire from the battery positive to the coil positive terminal. Then crank it and see if it starts.

Don't leave the wire on the coil a long time

 

[hubrvpete]

We upgraded to an electronic ignition when we put in the new engine. This is a non-vortec 350

 

[alldodge]

Try this, turn the key ON, and run a jumper wire from the battery positive to the coil positive terminal. Then crank it and see if it starts.

 

[PiratePast40]

Don't want to confuse things or send you on a wild goose chase, but wanted to relate what I just found on my boat. Was getting intermittent cranking. Sometimes just a click, sometimes turn over slowly, and other times turn over full speed. Checked voltages at each connector back to the solenoid. Finally determined that I had a bad connection at the engine wiring harness connector. Replaced the line from key switch to the solenoid and everything is fine now. Point being, and what others are getting at, is jumper around things and check voltages until you find the loss.

 

[hubrvpete]

Will try that tonight, thanks for all the help guys.