My engine is a 350 Volvo. Thought I had a bad fuel vent as I was losing top
end power after running for 5 minutes. Changed vents and went out again.
Same symptoms, run on step at 3500 rpm for 5 minutes then the rpm's drop
down to 2500 and it seems to run fine. I stopped and checked the
anti-siphon valve and fuel filter. After siting for 5 minutes cranked it up
to 3500 and it ran for maybe 30 seconds then dropped right down to 2500 or
so. No chugging, just slowly drops the rpm's like your backing down the
throttle. We stopped and trolled for a few hours - 2 king salmon and two
coho - then went to head back. This time it took several minutes to start
the main. After starting it would max out at the 2500 or so range. while
back in the harbor at idle it was running very rough and died just before we
docked and would not start agin.. I'm wondering if I have a bad coil? I
was going to start there and change the ingitor and resistor as well. These
were replaced 3 years ago. Where else should I look? New Carb and Fuel
pump last year - only have 40 hours on each. New plugs and plug wires as
well? Thanks in advance.

linus

It really doesn't sound like a fuel problem...but then, it could be...

If it were starving for fuel in a WOT situation, you would have backfires.
If it was loading up, that *could* cause your situation, but that thing
would have to really be dumping the gas, to bring you down from the top
RPMs.

Id take a quick look at the fuel system, but methinks you are on the right
track with the ignition.

Good luck.

--
-Netsock

"It's just about going fast...that's all..."
http://home.insight.rr.com/cgreen/

"Black-n-Gold" wrote in message
...
My engine is a 350 Volvo. Thought I had a bad fuel vent as I was losing
top
end power after running for 5 minutes. Changed vents and went out again.
Same symptoms, run on step at 3500 rpm for 5 minutes then the rpm's drop
down to 2500 and it seems to run fine. I stopped and checked the
anti-siphon valve and fuel filter. After siting for 5 minutes cranked it
up
to 3500 and it ran for maybe 30 seconds then dropped right down to 2500 or
so. No chugging, just slowly drops the rpm's like your backing down the
throttle. We stopped and trolled for a few hours - 2 king salmon and two
coho - then went to head back. This time it took several minutes to start
the main. After starting it would max out at the 2500 or so range. while
back in the harbor at idle it was running very rough and died just before
we
docked and would not start agin.. I'm wondering if I have a bad coil? I
was going to start there and change the ingitor and resistor as well.
These
were replaced 3 years ago. Where else should I look? New Carb and Fuel
pump last year - only have 40 hours on each. New plugs and plug wires as
well? Thanks in advance.

linus

Several years ago I experienced symptoms very similar to what you are
describing in my Mercruiser which was four years old at the time. It
certainly seemed like a fuel issue to me, and that's where I started;
anti-siphon valve, fuel pump, etc. The problem persisted; loss of
power at higher rpm only, after warming up only. Idle was fine. Then
I turned it over to my local pro, and he too was stumped for a while,
ended up getting the factory rep involved. Turned out to be an
ignition problem: specifically the "stator." Must admit I'm still not
sure what that is, but it did solve the problem. But I learned a
lesson about seizing on an assumption (fuel-related) and not keeping
an open mind to alternatives (ignition). Hope this helps, good luck.


"Black-n-Gold" wrote in message ...
My engine is a 350 Volvo. Thought I had a bad fuel vent as I was losing top
end power after running for 5 minutes. Changed vents and went out again.
Same symptoms, run on step at 3500 rpm for 5 minutes then the rpm's drop
down to 2500 and it seems to run fine. I stopped and checked the
anti-siphon valve and fuel filter. After siting for 5 minutes cranked it up
to 3500 and it ran for maybe 30 seconds then dropped right down to 2500 or
so. No chugging, just slowly drops the rpm's like your backing down the
throttle. We stopped and trolled for a few hours - 2 king salmon and two
coho - then went to head back. This time it took several minutes to start
the main. After starting it would max out at the 2500 or so range. while
back in the harbor at idle it was running very rough and died just before we
docked and would not start agin.. I'm wondering if I have a bad coil? I
was going to start there and change the ingitor and resistor as well. These
were replaced 3 years ago. Where else should I look? New Carb and Fuel
pump last year - only have 40 hours on each. New plugs and plug wires as
well? Thanks in advance.

linus

brad wrote:

Several years ago I experienced symptoms very similar to what you are
describing in my Mercruiser which was four years old at the time. It
certainly seemed like a fuel issue to me, and that's where I started;
anti-siphon valve, fuel pump, etc. The problem persisted; loss of
power at higher rpm only, after warming up only. Idle was fine. Then
I turned it over to my local pro, and he too was stumped for a while,
ended up getting the factory rep involved. Turned out to be an
ignition problem: specifically the "stator." Must admit I'm still not
sure what that is, but it did solve the problem. But I learned a
lesson about seizing on an assumption (fuel-related) and not keeping
an open mind to alternatives (ignition). Hope this helps, good luck.

[snip]
Greetings:

FWIW: The stator is the inductive pickup inside the distributor
of a system using an electronic ignition. It is essentially a pickup coil
that senses when a magnet comes near. The magnet is being rotated by it on
the distributor shaft as it turns.

There exists a similar failure mode to the regular ignition coil in
that sometimes there are intermittent internal shorts when hot. What happens
is that the insulation breaks down and allows some of the windings to short
out. The pickup unit inside the distributor is sealed with potting
compound, but can still exhibit this type of failure. It can be very
difficult to pin down.

The problem with nailing this is that the best way to troubleshoot
involves an ignition analyzer scope that can monitor the "dwell" period.
Think of the dwell adjustment on an old points type system. This dwell
period is what the pickup coil inside the distributor simulates. You will
only see this on the scope during the period when the problem is
manifesting itself, ie - not too many people are out boating with a scope
hooked up! :-)

It may or not be related to the particular problem at hand, I just
thought I'd throw it in for background. Good Luck to you in any event!

-Jason


--

PGP Fingerprint:Â*Â*CA481E501CCDAEA6DC28940488833E0887 E064D7

Classic mechanical fuel pump failure problem. Did it to me
,too. Finally solved it by replacing the pump.
JR

Black-n-Gold wrote:

My engine is a 350 Volvo. Thought I had a bad fuel vent as I was losing top
end power after running for 5 minutes. Changed vents and went out again.
Same symptoms, run on step at 3500 rpm for 5 minutes then the rpm's drop
down to 2500 and it seems to run fine. I stopped and checked the
anti-siphon valve and fuel filter. After siting for 5 minutes cranked it up
to 3500 and it ran for maybe 30 seconds then dropped right down to 2500 or
so. No chugging, just slowly drops the rpm's like your backing down the
throttle. We stopped and trolled for a few hours - 2 king salmon and two
coho - then went to head back. This time it took several minutes to start
the main. After starting it would max out at the 2500 or so range. while
back in the harbor at idle it was running very rough and died just before we
docked and would not start agin.. I'm wondering if I have a bad coil? I
was going to start there and change the ingitor and resistor as well. These
were replaced 3 years ago. Where else should I look? New Carb and Fuel
pump last year - only have 40 hours on each. New plugs and plug wires as
well? Thanks in advance.

linus

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JR,

I was thinking about this as well. I discounted though after it took me so
long to start after we ran - I was getting plenty of gas in the carb. This
is what made me think about ignition.


"JR North" wrote in message
...
Classic mechanical fuel pump failure problem. Did it to me
,too. Finally solved it by replacing the pump.
JR

Black-n-Gold wrote:

My engine is a 350 Volvo. Thought I had a bad fuel vent as I was losing
top
end power after running for 5 minutes. Changed vents and went out
again.
Same symptoms, run on step at 3500 rpm for 5 minutes then the rpm's drop
down to 2500 and it seems to run fine. I stopped and checked the
anti-siphon valve and fuel filter. After siting for 5 minutes cranked
it up
to 3500 and it ran for maybe 30 seconds then dropped right down to 2500
or
so. No chugging, just slowly drops the rpm's like your backing down the
throttle. We stopped and trolled for a few hours - 2 king salmon and
two
coho - then went to head back. This time it took several minutes to
start
the main. After starting it would max out at the 2500 or so range.
while
back in the harbor at idle it was running very rough and died just
before we
docked and would not start agin.. I'm wondering if I have a bad coil?
I
was going to start there and change the ingitor and resistor as well.
These
were replaced 3 years ago. Where else should I look? New Carb and Fuel
pump last year - only have 40 hours on each. New plugs and plug wires
as
well? Thanks in advance.

linus

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Remove X to reply

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Home Page: http://www.seanet.com/~jasonrnorth