470 poor starting after rebuild

[Rake722]

Aside from the tarter bypass - if I understand correctly, I have cut the resistor wire at the choke and run a new wire from the switched 12V at the choke to the positive post on the coil to remove the resistor circuit - but - I have left the resistor wire in at the coil.

If as some users suggest, the resistor wire originates in the harness NOT the choke then could it be that I am still getting less than 12 v at the coil ?

I'll remove this wire from the coil and re test.
I can also use the original coil with the resistor wire present to see if that fixes it.

 

[achris]

A Q&D way to see if the 'bypass' is the problem. Next time you want to start the engine, put a jumper wire from the battery + to the coil + and see if it starts any better. If it does, bypass may be your solution, if not, it's one more thing you have ruled out.

Chris......

 

[stonyloam]

On the 470 you should have a wire running from the slave to the coil + that bypasses the resistance wire, however if you have replaced the resistance wire it should not make any difference because the coil is getting 12v all the time, but you still should be getting battery voltage from the slave too when starting. I would reset the timing to 8° BTDC. Yeah throttle setting can be a little tricky, I need to pump mine twice, then set the throttle to about 1/3 then it will start. Try some different throttle settings.
one additional thing that I did with my Petronix is add a relay (similar to a electric fuel pump relay) that is activated by the wire from the choke that feeds voltage directly from the hot side of the slave to the coil +. This assures you are getting full voltage and current to the coil when the ignition switch is on. This bypasses the long run from the ignition switch.

 

[achris]

...one additional thing that I did with my Petronix is add a relay (similar to a electric fuel pump relay)....

:thumb:

 

[Rake722]

Got down to the boat yard today and did as you suggested I put a jumper wire between battery positive and coil and she fired right up.

I then Removed the jumper wire and measured the voltage at the coil positive post while cranking the engine. Result was 9v while cranking.

I then did exactly the same test with the jumper wire on the starter solenoid purple yellow post and the result was saying nine volts while cranking

is it normal or does this indicate a problem with either the solenoid or purple yellow bypass wire ?

She started most of the time today update it later and she likes to be started with the throttle wide open

 

[achris]

9v while cranking is low. Your battery is weak. Replace. Shouldn't drop below 10v.

 

[Rake722]

Chris - I hear you but the cell is only a year old and 1000 amp hr but I did suspect a low battery. Took it home slow charged and put her back in.

so I should see a voltage drop on cranking - that’s what I needed to know.

id just love this motor to start on first or second rotation of the engine rather than having to crank for so long and set WOT to get a start.

thanks again

 

[stonyloam]

Two things: check the battery voltage directly on the + post while cranking, if it is the same 9v you have a battery or starter problem. If so take the battery out and charge it fully and take it to a service canter to have them do a load test on it. New starter right? So that should be OK, but you never know.
Oh yeah, this is a conventional carbureted engine so they just require more cranking to get going. I think we get a little spoiled because our fuel injected auto engines start almost instantly, especially young guys that have never gone out on a cold winter morning to crank over the “57”

 

[Rake722]

Thanks Terry,

Looks like I may have a starter issue then - its the old prestolite not a new one - I already had the battery tested and they said it was good so I brought it home and slow charged it for 24 hours.

Whislt im not a geriatric I am close to 50 so had the older style engines in my early years - granted - the new ones start alot quicker.

I definatly have 9V at the post on cranking, it actually drops below 9 then comes back up to 9 after cranking a little.

Could it be a solenoid issue or definatly starter related if not battery ?

 

[achris]

Look for voltage drops between the battery and the starter, and don't for get the negative side...

Put the positive lead of the multimeter on the battery positive post, and the multimeter negative lead on the starter post. Crank the engine. Do the same on the negative side, one lead on the negative battery post (not the terminal, the actual post) and the other lead on the starter case... You need to see a combined voltage drop less than 1/2v .

If everything is ok, then the starter is suspect.

Chris......

 

[Rake722]

Thank you. One point to not is that my battery negative lead goes direct to the starter negative post - I take it that I have it correctly connected

 

[stonyloam]

If you consider a new starter look at a permanent magnet gear reduction (PMGR) starter. About $80 on eBay. I went to one years ago and really like it. It is very compact and easy to install.

 

[Rake722]

Yes the one that broke its nose was a PMGR. Alas it has gone to starter heaven now.

 

[kenny nunez]

The Prestolite starters gave the most trouble, they tend to “drag” where the bushings wear and the armature rubs against the pole shoes, the other problem is with the Bendix drive where it kicks out early doing what is called a “false start”. This also causes the flywheel teeth to get broken.
To convert to the Delco style requires a pair of stepped studs which are 1/2” 13 X 7/16 20 and new nuts which was in the kit that Mercruiser had, maybe the kit is still available. It came with some new wires and directions to connect the boost solenoid to the main starter solenoid. The Delco style will be the best and most trouble free, if you get one just be sure that the drive is not a rebuilt instead of a new one. Rebuilt starter drives also can damage the flywheel.

 

[Rake722]

I hear you on that Kenny as I think I heard some not so normal sounds while cranking. Sounded like that false start.

in addition starting seems laboured very soon after a few good spins it slows right down

 

[stonyloam]

Yeah sounds like Kenny is onto the problem. Had the same happen to me. When the armature rubs it really slows the starter and puts a huge current drain on the battery. The 470 starter armature is quite long and can also bend and cause a rub ( I think that was my problem), same result.

 

[achris]

..... When the armature rubs it ....

That is called 'poling'....

Chris.........

 

[kenny nunez]

“Poling” here in Louisiana is how the Cajuns propel their Pirouges and Bateaus in the bayous.

 

[Lou C]

Hank Williams...On The Bayou....

 

[achris]

“Poling” here in Louisiana is how the Cajuns propel their Pirouges and Bateaus in the bayous.