4.3 omc cobra no start

[Lou C]

The other reason why in this case I'm advising self-teaching is this:
you have an OMC drive system on your boat. OMC went out of business 20 years ago and very few shops will work on these. Its not like a Mercrusier where there is a mechanic in every town that has boating resources, you have to be your own mechanic much of the time, to keep it going. So I have books, tools, and plenty of spare parts....

 

[Scott Danforth]

once you lean the diagnostic skills and mechanical and electrical prowess of working on a points ignited carbureted motor, the same theories help diagnose today's vehicles. Having the manual shows you the procedures the factory deemed required. however having the base knowledge of the otto cycle and how points ignitions work is required prior to grabbing the manual.

there is not much to suck-squish-bang-blow once you understand and know the basics.

 

[Lou C]

that's why I posted the second book, it goes through all that, how points saturate the coil to step up the voltage and how point gap and dwell interact with that...
let's all really learn instead of waiting for sound bytes without understanding theory...


Stone age technology that still works and won't strand you because an NLA mystery box went poof. Keep spares and tools on the boat and you'll always get back....

 

[Xlanci]

Thank you I’m very greatfull to get to learn from you all

Thanks to everyone’s help snd advise I finally got it running now I just have to find a wiring diagram for some of the electronics and should be all good to go just want to thank y’all again definitely would’ve been stumped for a
Whole if not for all the advice

 

[Scott Danforth]

Now that it is running, please share what it was that was preventing it from running so future readers can learn about the steps you went thru and what it was you found.

 

[Xlanci]

Now that it is running, please share what it was that was preventing it from running so future readers can learn about the steps you went thru and what it was you found.

Alright so it was actually a few things first off I did a starter replacement but it only had a 3 terminal solenoid you need a 4 terminal solenoid for this system for batt,starter,coil and the constant coil wire that kicks on after the initial start to keep it running then it was my points pickup wire going to the - coil terminal had a faulty connection and then it was the dwell I kept making the gap smaller cause I thought a Lower dwell number meant it had to large of a gap but then once I enlarged the gap it hit the appropriate dwell angle dead on abd starter right up but did have that solenoid problem that cause it to die right after it started

 

[Xlanci]

Alright so it was actually a few things first off I did a starter replacement but it only had a 3 terminal solenoid you need a 4 terminal solenoid for this system for batt,starter,coil and the constant coil wire that kicks on after the initial start to keep it running then it was my points pickup wire going to the - coil terminal had a faulty connection and then it was the dwell I kept making the gap smaller cause I thought a Lower dwell number meant it had to large of a gap but then once I enlarged the gap it hit the appropriate dwell angle dead on abd starter right up but did have that solenoid problem that cause it to die right after it started

Can someone please explain how the omc out drive work for cooling like i know the water from the bottom comes to the top where the water pump is but where does it go after that and where would the hot water spit out also does it need to have the gear case water pump cover on for it to run cause I believe I have a over heating problem but not sure cause the temp gauges goes green the alittle white and my arrow is in the white so is that the overheating line or am I reading it wrong

 

[alldodge]

To find out if the motor is actually over heating, get a IR temp gun. Take measurements on the thermostat housing and compare with the boat gauge

From the drive thru a power steering cooler (if it has one)
Then to thermostat housing
T housing to engine circulating water
C water pump to engine block and to exhaust manifold and or exhaust elbows
When thermostat opens hot water goes out thru exhaust and cooler water goes into engine block

This is not an OMC but can give you the basics

 

[Lou C]

Ok on this engine the cooling water is pumped up from the water intakes thru the pivot mount then it gets pumped thru the transom mount. Next it flows thru the P/S cooler on the back of the engine then flows forward to the thermostat housing. The cool water initially flows out the exhaust manifolds until the thermostat opens and allows hot water to flow out of the intake manifold to the exhaust. Then the incoming cool water gets sucked into the engine via the front circulating pump & picks up the heat from the block & cyl heads then flows out the intake manifold to the exhaust. The thermostat opens just enough to maintain a running temp of 160-175*. It’s a pretty simple system. Impellers are very easy to change and usually last at least 3 seasons. Start with the impeller if the old one is missing pieces the P/S cooler could be clogged with them or even the thermostat housing. So impeller, P/S cooler and stat housing should be checked.

 

[Xlanci]

Ok on this engine the cooling water is pumped up from the water intakes thru the pivot mount then it gets pumped thru the transom mount. Next it flows thru the P/S cooler on the back of the engine then flows forward to the thermostat housing. The cool water initially flows out the exhaust manifolds until the thermostat opens and allows hot water to flow out of the intake manifold to the exhaust. Then the incoming cool water gets sucked into the engine via the front circulating pump & picks up the heat from the block & cyl heads then flows out the intake manifold to the exhaust. The thermostat opens just enough to maintain a running temp of 160-175*. It’s a pretty simple system. Impellers are very easy to change and usually last at least 3 seasons. Start with the impeller if the old one is missing pieces the P/S cooler could be clogged with them or even the thermostat housing. So impeller, P/S cooler and stat housing should be checked.

Thank you both a lot that’s exactly what I was looking for and more ill try y’all’s advice tomorrow and let ya know how it goes

 

[Lou C]

Water exits from under the transom mount at idle on the water muffs…

 

[Xlanci]

Water exits from under the transom mount at idle on the water muffs…

It turned out to just be the water pump luckily, now she’s up and running great can’t believe how much different this boat is now thanks to all of y’all’s help

 

[Lou C]

great work!

 

[Xlanci]

great work!

Hey guys this isn’t about the same boat but was just curious if any of you knew if it was possible to convert an engine that takes coolant and freshwater to cool it down to just fresh water if your wondering the engine is a 470 merc I’d be interested to know if anyone’s ever tried that or knows how to go about it

 

[Lou C]

Try posting your question up on the Merc I/O forum, I'm sure someone will know.

 

[Xlanci]

Try posting your question up on the Merc I/O forum, I'm sure someone will know.

Preciate I’ll try that

 

[Bondo]

Hey guys this isn’t about the same boat but was just curious if any of you knew if it was possible to convert an engine that takes coolant and freshwater to cool it down to just fresh water if your wondering the engine is a 470 merc I’d be interested to know if anyone’s ever tried that or knows how to go about it

Nope,.... Not that motor,......

It was a pos the day it was built, you don't want anything to do with a 470,.....

 

[Lou C]

Isn't that the Merc combination of a cast aluminum block and cast iron Ford 460 head? with closed cooling because of the alu block?
I think you'd be better off with a 4.3 in every way!