Hello,

This is my first post here. I posted over at iboats and was told that the members here may have a bit more insight.

Background: I recently bought a 2003 chris craft with a 8.1 gxi motor 300 hours with a whipple 2300ax supercharger setup. Had a mechanic give it the all clear before I bought it. As soon as I purchased it, I had the shipyard do the yearly on it. Plugs, oil, etc. Now, I have run the thing for about 5 hours took it out last weekend and cruised at 4000 rpm for about 15 minutes. Pulled the throttle back at the mouth of the harbor and I start getting the audible alarm every 4 or 5 seconds and it starts running rough. The gauges all look good. The oil is good. The temp is good fuel pressure is fine. I open the hatch and the engine looks fine. I have a hard time getting it started, I had to take it out of gear and give it throttle to get it to turn over. Then I limped back to the slip in 10 minutes with the alarm going off every 5 seconds and the boat running like crap. Shut it off and go home.

The next morning, I go to fire it up and again, I need to take it out of gear and give it gas to get it going. Once it turns over, a big black cloud of smoke comes out of the exhaust as well as soot into the water. As the engine warmed up, I was able to pull the throttle back until it was in neutral and idling normally. I cut the engine and then refined it as nothing had happened. I tooled around the harbor that afternoon, stopping and starting with no issue.

Lastly, there was one minor detail I forgot to mention, a few runs before this, the motor spit the raw water pump off the front of the crankshaft a few runs ago. Shut down immediately, checked compression and all was fine. No water in the oil. Got a new pump and added coolant.

My question is simply, what happened? Did I break something? Does this happen from time to time?

Thanks for your help on this.

Most likely your IAC is going bad.

Very possible. Common problem on the 496 engines. Mine went bad at the end of last summer. Very hard to tell without the ECM being scanned to see what fault code is present. You need to have it scanned or buy your own scan tool via Rinda.com. Volvo uses the MEFI 4 ECM in this application. Being that you are experiencing the alarm indicates a fault being seen by the ECM.

Have it scanned and get back to us..

As Ryan said its worth buying the scan tool. It will save you thousands int he long run.

-The easiest thing to do is scan it...
If you want to go at it here are a few things to check
-Take the IAC to the local NAPA tell them its a 496/8.1 truck engine. Dont mention boat or they will freak out. That is a cheap fast easy fix if it is the problem.
-Running crappy could be the camshaft position sensor. 496's have been know to have the issue int he past.
-Check to see if the fuel filter is new. Maybe you have some bad gas from last year.
-Not probable, but check a plugs they put in. Make sure its the right plug and make sure all the plug wires are pushed on till they click. Its actually pretty hard to do in some spots.

I agree with the above. Also verify the plugs used are the correct ones that Whipple recommends. They are not the same heat range as the stock 496 plug. Is probably not the problem but could result in big problems down the road when a piston lets go. With the Whipple kit on a stock internal 496, everything has to be spot on..

Take caution on some of the advice above. The 8.1 GXI motor is a Volvo, and while many things are the same on a Mercruiser 496 HO/Mag; many things are different as well.

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I agree, that it could likely be an IAC going south. But if the motor is beeping, it's yearning to tell you something. Get a scanner, or have it scanned by a mechanic and let it speak to you.

YOU ARE RIGHT!


The OP might have a MEFI 4 (which is good). I am pretty sure the Volvos didnt have PCU 555 at all.

There is no telling what you may have working here. There are product id numbers on your ecu it would be of extreme help for you to post them done take for granted that's a mefi on your boat.....Mefi 3 should give you a high idle with a bad iac i dont believe you would get a alarm with that system for a iac....Ive had mine unhooked more that once thourgh careless and in a rush work.

Volvo Penta in 2003 used MEFI 4 in late 2004 all Volvos went to E- controls ECM's. They still currently use E-Controls. Volvo use MEFI 1,& 3 and 4 never had MEFI 2 they stayed with MEFI until MEFI 3 came about.

The only thing that the Volvo 8.1 shares exactly with the Mercruiser 8.1 is the Longblock. Also a lot of Volvo 8.1 did not use close cooling it was an option. All Mercruiser 8.1 use closed cooling. Just for another comparsion FYI

IAC can be the problem BUT Volvo Penta does not have near the problems as the Mercruiser FORD IAC. Volvo IAC below GM Style. I am not saying your IAC is good either - you need a scan it with Vodia or Diacom.

Next ALL MEFI 3 do not support coil over spark plug ignition. MEFI 4 started for Volvo 2001 for the 8.1 in which MEFI 4 can drive 8 coils controlling spark advance at each cylinder.

VOLVO IAC below for MEFI 4 - 8.1

http://www.michiganmotorz.com/mercru...ve-p-1247.html