Check the firing order. 5.0L and 5.8L marine are 1-3-7-2-6-5-4-8. Also
check your plug wires. Make sure one is not arcing to the manifold, etc.
Bill

"ClassicBoat" wrote in message
news
On 9 Jul 2003 04:04:03 -0700, (GVB) wrote:

Throttle pump arm is good.
Distrib cap is new.
Timing set at 10* BTDC running 89 octane.
Ballast resistor was bypassed as part of the ignition kit install.
I'll double check the voltage at the coil to make sure I'm getting
12v.

Any other ideas? Keep in mind that when I first start the boat, let
it warm up to operating temperatures and run it, it runs fine, but
won't get up to top speed.

Once it's been on and under light load for about 10 minutes, the
issues begin. Sputtering/Bogging down at low rpm, etc...

Thanks!

"Calif Bill" wrote in message
...
"Ron White" wrote in message
...
It could be the ignition wire, the wire from the ignition switch to
the
coil. To test for this, just place a jumper from the coil to a good
hot
source like the battery or starter lug. Of course this can be
dangerous
because you cannot turn off the engine without removing the wire.
Oddly , this can cause bad running if this goes bad. sounds like you
have
done most of the things that you would normally suspect, so try that.



As to the hesitation, pull the throttle pump activating arm. the one
that
rides on the cam and clean and grease the pivot post. Mine, gets rust
on
the post and the throttle pump barely moves. Check that the
distributor cap
is not cracked. The Ford Power Products bulletin #200 June 1966 says
to set
the timing 2 degrees BTC if running 87 Octane and 10 degrees if running
89+
octane. With the Electronic ignition (Petronics?) try running 12 volts
to
the coil and bypass the dropping (ballast) resistor. Mine got some
corrosion somewhere in the wiring and was only running 5 volts at the
coil.
I find the NGK plugs run the best. Do not use Motocraft. They are not
plated and rust to the holes very quickly.
Bill

You seem to have covered most bases. The specific problem I keep
trying to reconcile is the backfiring. Since you seem to have done
everything to insure fuel getting to the cylinders and a hot spark, if
the latest carb soaking attempt doesn't fix the problem I'd look at
the (admittedly somewhat remote) possibility of sticking valves.

on some engines with electonic ignition you need a "scan" tool to put
the electronic ignition "brain" into some kind of "service" mode
*before* you can set the timing with a timing light.

is yours like that?

I triple checked the firing order, its good to go. Plug wires look
OK. I checked for arcing in the when the sun went down... looks good.

I dropped the boat in the water this morning. Re-cleaning the
metering block didn't fix the problem, it was still stumbling at low
rpm. Tried the easiest thing first, put in the old coil. And it
seems to have fixed the stumbling at low RPM problem!! The old coil
has fluid in it, the new one doesn't. Was the old coil a marine
specific coil or something that prevented overheating? Or did I just
get a bad coil?

There is still a little bit of hesitation upon hard acceleration, but
I am guessing that I can adjust the accelerator pump to push more gas
through? I don't know carb adjustments very well.

And I still can't get it over 4000 rpm.

Any other thoughts on these other two problems?

Thanks everybody.

(GVB) wrote in message om...
I bought a 1989 MasterCraft Pro Star 190 w/ Indmar Ford 351 motor.
While test driving the boat would hesitate and backfire when jumping
on the throttle from an idle, but ran fine otherwise. Didn't think
much of it and ended up buying the boat.

Changed oil and filter.
Changed plugs.
Changed water seperator filter.
Changed fuel filter.

* Took it back out in the water and it ran the same.

Installed a breakerless ignition kit (replaces the points and
condenser with a magnetic pickup).
Replaced the distributor advance springs with new ones that came with
the kit.
Replaced cap and rotor.
Replaced ignition coil.
Set timing to 10* before TDC.

* Took it back out in the water and it still backfired, but not as
much. The hesitation problem was still there. But now I couldn't get
it past 4000 rpm (should top out around 4500-4800). And the motor
would stumble at any constant speed below 2000 rpm. It seemed to get
worse as the longer the boat was running. When trying to get it up on
the trailer it kept stalling.

Put the old distributor advance springs back on.
Rebuilt the carberator.
Reset timing.

* Just took it back out on the water today and I am still having the
same problems, although the backfiring is gone.

We rebuilt the carb using lacquer thinner and someone recommended
taking the metering block back out of the carb and soak it in carb
cleaner for a day or so because lacquer thinner doesnt disolve gas
deposits and buildup like carb cleaner does. This person (reputable)
seemed to think that the symptoms still sound like a typical carb
problem.

So the metering block is in the garage soaking. I also had plans to
drop the boat in the water tomorrow and try putting the points
ignition, cap/rotor, and old coil back on and see if that helps.

Can anyone think of anything else I should be looking at to try and
solve this? I havn't measured the resistance of the plug wires, but
they look pretty new. Possible fuel pump problem?

Thanks in advance.

"RG" wrote in message news:XG1Pa.46$Bp2.17@fed1read07...

Possible that the magnetic pickup in the new breakerless ignition kit is
defective out of the box? I say this because your symptoms are identical to
symptoms I had when the magnetic pickups in both my MerCruiser GM 5.7's
failed. Engines would run fine before they came up to full operating
temperature, but once the engines came up to full temp, the magnetic
ignition module in the distributor would start to fail. The engines would
stumble and stall at low RPM, and would cough and backfire at higher RPM.
Acted just like it was starving for fuel. Eventually they would be
impossible to restart. Once the engine cooled off, everything was just fine
again. Drove me crazy trying to figure it out. The diagnostic test is to
take a voltmeter to each of the two wires coming and going to the module.
You should see the same voltage coming out as going in. As my engines
warmed up I could watch the output voltage gradually drop from 12+V to
almost zero. Do the test while your engine is cold for a baseline
reference, then test again once the engine starts to run poorly and compare
the results. My modules failed within 10 operating hours of each other on
both engines. Couldn't believe it.

I realize that we are talking about two entirely different engines from two
different manufacturers, but the symptoms sure sound similar, and if we are
talking about the same part, I bet they are very similar in their function.
The part I am referring to is inside the distributor and is held to the base
of the distributor with two screws. Metal vanes from the rotor pass through
the gap in the sensor module, generating a pulse that essentially performs
the same function as ignition points. Turns out that the heat rising from
the engine would cause the modules to heat up and temporarily short out at
high temperatures. Fairly common problem on the MerCruisers, I later found
out.

RG,

Thanks for the tip!! I will call skidim.com tomorrow and see if they
can send me out another kit to test with.

I will be out on the water again tomorrow to make sure the boat is
ready to go for this weekend. I will measure the voltage coming from
the magentic pickup (yes, we are both talking about the same thing)
and make sure it stays constant and doesn't drop as it heats up.

Thanks again.