Volvo Penta 5.7gsi running rich

[m_schro]

I have a 2000 Four Winns with a 5.7gsi. I purchased last year and I am relatively new to the boating community. The motor runs rich at idle, so much so that black soot stains the hull at the water line. I examined the engine to find that the vacuum line going to the MAP sensor had been capped off and the MAP sensor vacuum barb was broken. I ordered a new MAP sensor thinking I had found the problem. I put the sensor on today and with the vacuum line connected it idles at over 2000 rpm, if i cap the vacuum line it drops to 800ish. Any ideas on what I have going on? Thanks

 

[BILL INGRAHAM]

Re: Volvo Penta 5.7gsi running rich

r u TBI ?did someone try to compensate your idle some how not knowing the map unit was critical.

 

[m_schro]

Re: Volvo Penta 5.7gsi running rich

Yes, it is TBI. It is possible that some other sensor failed or something happened and someone disconnected the vacuum line from the MAP sensor to drop the idle. Last summer I tested the compression and everything was fine, but when I tested the vacuum I got low but steady readings. If I had low vacuum at idle would that trick the MAP sensor and cause the high idle? The hour meter reads 114hrs, so I dont think I have a worn timing belt, and I could not find any vacuum leaks, so I am not sure what is going on with the vacuum readings. The engine fires every time and runs smooth without he MAP sensor connected, but at idle it there so much black soot coming from the exhaust it floats on the water and stains the hull. At higher RPM I do not notice the soot. At WOT I hit approx 4000-4100 RPM, a little short of what the manual says (with MAP disconnected). Any Ideas?

 

[BILL INGRAHAM]

Re: Volvo Penta 5.7gsi running rich

i have similar set up to yours -2000 VOLVO PENTA 5.0 GI PEFS TBI fresh water cooled with TSK SX-M transom and DPS-M 1:95 drive. the map sensor is imperative for proper fuel management-i still think someone has monkey rigged your tbi to raise the idle not knowing.look over your tbi real carefully for any signs of tampering.