BUP

iTrader: (9)

Brian, Ok thx and I have a brand new old one coming from a source to see what needs to be done here.

Knot 4 Me

PM sent.

4Lance

Anything new here? Im having similar issue 496 ho 2003 boat surging

BUP

iTrader: (9)

Sounds like an IAC problem and or a fuel problem It would be wise to scan your app and take fuel pressure readings before jumping the gun about the cam sensor.

Will add about sensors on the 496 the worst in this order for being a problem child Top 4 in that order.
1. IAC
2. Water Pressure sensor
3. Crank PS
4. Exhaust manifold temp sensors

Non sensor related but hurts idle and longevity of the IAC
1. Dirty flame arrestor
2, clogged / dirty IAC Muffler
3. Dirty clogged IAC muffler cavity.

Also heat hurts the IAC over time especially longer durations of 100 duty cycles. The more the IAC has to readjusts and or calculates its positions the less it will last. Proper air flow is important here also, good clean air flow.

Next fact is all Mercruiser DTS engines that are ECM & PCM 555 computer controlled DO NOT have a IAC nor an IAC muffler or its cavity to sit in. The DTS system adjusts the throttle plate for correct idle speed from output signals the computer is reporting. Again DTS = digital throttle & shift no IAC or related IAC parts. FYI

Sydwayz

iTrader: (1)

Any beeps or codes?
Surging at idle or at what RPM? Not enough info to go on.

4Lance

Ok I just got the finda techmate pro srill have to figure out how to use this. Fuel psi was 43-45 key on and idle and also when vact line is pulled from fuel pres regulator. When the engine surges and drops rpms then revs back up to where it was fuel psi doesnt drop thst I see and sure doesnt drop below 40psi. I changed IAC still does it. Swapped sensors on center of manifold to see if it went away . Changed fuel filter sep......

Iac didnt look dirty looking into throttle body there isnt any filter stuffed in hole

I changed the iac with the napa 2002 ford windstar even came up on their computer fits mercruiser 496 ho and they look exactly the same just not painted black doesnt come with correct gasket used black rvt in a pinch

Sydwayz

iTrader: (1)

If you have beeps/codes, you must get to the bottom of this first.

Do you have the "D-cell battery looking" inline fuel filters? I venture to say this is not the problem, since your fuel pressure sound fine; but I would replace them if they have been on there a while.

4Lance

Also when it surges its anytime at idle or also in gear ....does it mainly once to normal operating temp. Think it does it all the way up to 2000rpms because I can take off get on plane and runs fine but once back down to idle it starts surging this engine is also running hotter but I have a low water pickup only drive on it for now til I find a bravo x drive broke a gear in lower unit then they said upper was bad needed new drive got one used from shop for 1000$ anyways then my starter went out on this same engine just sitting at the dock would just spin but wouldnt try to crank ect. They installed new starter. And starts right up now everytime. But they did have to take off the exhaust manifold to replace starter. Cant think of anything they would have done but this idle surging issue came up after starter was replaced

4Lance

I dont see these inline filters? All I see is fuel water sep spin on. Then there is a fuel pump behind it

Sydwayz

iTrader: (1)

They look like this:
http://www.wixfilters.com/Lookup/Par...spx?Part=33481
...and would be between your fuel tank(s) and the F/W separator somewhere.

There is also a screen on your boost pump that could become clogged, but I don't think that is your problem either.
If you have beeps and/or codes, it's more than likely a sensor problem. not a fuel problem.

Good threads:
http://www.offshoreonly.com/forums/g...el-filter.html
http://www.offshoreonly.com/forums/d...esitation.html
http://www.offshoreonly.com/forums/g...en-stalls.html