mercruiser 3.7 misses then quits

[arnold p]

I have 1989 3.7 L mercruiser ,after 20 -30 min.running at 3500 rpm started to miss then ,what feels like running on 3 cyl, then 2,then on 1 ,the quits.Took it to mercruiser tech,and after sea trials,he said coil was getting hot ,too many votls going to it.He put new resistor wire ,to carry the 9 volts it needs,and new coil,and points.This lasted about 8 hours off boating.Here are some readings (700 rpm- 11.4volts) (1600 rpm - 12 volts)(2000 rpm -12 volts)(3500 rpm - 12.4 volts).
So as an easy fix (i though) i when with a PerTronix's Ignitor ll and theFlame-Thrower ll coil,(epoxy filled). So to make it easy i ran the postive wire straight to the battrey to get the 12 volts which it needs to run.It started right up and ran at 3500 rpm for 20 min and then guit.Can soneone help me

 

[Bt Doctur]

Re: mercruiser 3.7 misses then quits

When it quits do you have spark or any power to the coil?

 

[Don S]

Re: mercruiser 3.7 misses then quits

Sounds like you have something plugged in the fuel system.
Read the thread at the link below, and do the tests, I think you will find your problem.

http://forums.iboats.com/showthread.php?t=167561

 

[arnold p]

Re: mercruiser 3.7 misses then quits

yes it will start,but you can only idle along.If you give it to much fuel it will start to backfire,and run rought

 

[Bondo]

Re: mercruiser 3.7 misses then quits

If you give it to much fuel it will start to backfire,

Ayuh,...... That's Because it's trying to run LEAN.......

Your carb needs to be torn down, Soaked, Cleaned,+ Possibly it will live again with a full Rebuild.......

 

[arnold p]

Re: mercruiser 3.7 misses then quits

fuel system was all checked,valcum,fuel pump,pressure,service tech. even used a different fuel tank. Tech had boat for 1 week.and i got big bill.

 

[Bondo]

Re: mercruiser 3.7 misses then quits

fuel system was all checked,valcum,fuel pump,pressure,service tech. even used a different fuel tank. Tech had boat for 1 week.and i got big bill.

Ayuh,.....

You don't say "Carb Rebuild"........
And,.....
Rebuilding an old carb is at best a 50/ 50 proposition.........

You might need a Replacement Carb......

 

[arnold p]

Re: mercruiser 3.7 misses then quits

this does not answer the reason for the high voltage readings,i thinging now that all the trouble mint be with my water cooled voltage regulator,because once you let it cool down it runs good for another 20 min

 

[Bondo]

Re: mercruiser 3.7 misses then quits

)(3500 rpm - 12.4 volts).

Well,..........

At anything over Idle you should be seeing 13.6 Volts.......

If anything you're running Low Voltage.........

You can run around in circles,...... Or,......Look to the Problem........

Backfires are caused by a Lean Condition.........

 

[JustJason]

Re: mercruiser 3.7 misses then quits

I'll double what Bondo said....
The ignition system has nothing to do with a "lean pop". The fuel is igniting itself because it is flowing to lean... (or not enough fuel), the motor needs to have the right amount of fuel. Your better off... and safer, have a bit to much rather than a bit to little.


Just for giggles do a compression test...

 

[capecodder116]

Re: mercruiser 3.7 misses then quits

This is de ja vu for me....I had same issues with my 1984 260 mercrusier. It would run strong for 1/2 hour or 1/2 day, then engine would start to slowly loose rpms until it would just idle. Try to give it more throttle and she'd die.

Bought vaccum gauges, everything check out, bypassed my fuel tank with a 6 gallon jerry jug, rode around in circles for hours trying to make the engine act up. I replaced coil, checked fuel lines, replaced fuel pump, hose clamps, you name it I tried it.

Never figured it would be the carb as I thought, "engine runs great then all of a sudden just slowly starts to loose rpms", can't be the carb?

Next time I experienced the problem, I immediately went to the carb and operated the throttle manually while looking down the throat of the carb. Guess what..??? No fuel squirting in..!!!

Botom line....had the carb rebuilt and even though I was told it was "clean inside"...knock on wood, last summer was the first summer in 3 years that I did not experience the problem.

Have the carb rebuilt and save yourself the aggrevation....Trust me..!!

 

[arnold p]

Re: mercruiser 3.7 misses then quits

i will have carb rebuilt,but still cannot understand why,when i got boat back from service tech i when on a 2 hr run and everything was all right.Something must be breaking down my resistor wire,to have those high readings on the + side of coil (up to 12.4)when it is running.I understand that when you turn the key to srart it sends 12v and when it starts and you let go of key it goes back to 9v.Something must be breaking down my resistor wire for this to happen.

 

[arnold p]

Re: mercruiser 3.7 misses then quits

Still can't figure out why resistor wire going to coil ,goes bad (if it is bad)or why it is carrying 12volts to coil after it starts.

 

[Bondo]

Re: mercruiser 3.7 misses then quits

Ayuh,....

If you think that's the Problem,.....
Go to a Parts House,+ grab a Ballast Resistor to install in the wire, before the Coil.....

 

[Don S]

Re: mercruiser 3.7 misses then quits

Even if you had 15 volts to the plus side of the coil, it wouldn't cause your problem. It would burn the points up in no time and it would quit running, and will not restart.

 

[Coors]

Re: mercruiser 3.7 misses then quits

Like Don said- solve your fuel problem first, then trouble shoot the voltage.
They are 2 complete different things.

 

[bigbrownbuku]

Re: mercruiser 3.7 misses then quits

Well,..........

At anything over Idle you should be seeing 13.6 Volts.......

If anything you're running Low Voltage.........

You can run around in circles,...... Or,......Look to the Problem........

Backfires are caused by a Lean Condition.........

a bad ignitor will also cause a backfire, heck any bad pickup could cause a backfire. ive seen bad pickups and ignitors straight out of the box with a missing pickup 7 instead of 8 that kind of bs. if i thought i could get away with saying the "b" word i woulda sent a letter "b" to the ignitor factory that day.

that being said....when the motor breaks down next lift the hatch and listen very carefully to your carb, yes listen, you should not hear any hissing or what may sound like boiling.

does pertronix make a 9volt flamethrower? read the instructions very carefully in that ignitor box. dont deviate at all and it will work fine, if you have a resistor remove it and wire it like it tells you too.

 

[Bondo]

Re: mercruiser 3.7 misses then quits

Ayuh,.....

Not to argue your point BBBk,..... 'cause I agree in principle,....

But,......
Arnold had this Issue with the old Points before he installed the Pertronix.......

Which is Why I believe he's fighting a Fuel related Issue......

 

[Pattie]

Re: mercruiser 3.7 misses then quits

Had to replace my voltage reg. a couple months back, but that's not the prob you're having.