Volvo Penta 5.7GSi Running Rich, Strong fuel smell

[TimoLKN]

Hey everyone,

I recently acquired a 1998 Forumla 280 SS with twin VP 5.7GSi TBI engines (5.7GSIPLKE) and Bravo 3 dual prop outdrives. I have been working on restoring the boat for a couple months now as it lived a rough life between fresh water, to salt water, to sitting for 5 years in dry storage before I acquired it. When starting the boat, the port motor starts and runs fine; however, the starboard engine starts, but it idles very rough and when given any throttle it dumps black smoke out the back and smells strongly of gas. When I consulted with a local mechanic he believed it was the IAC. I replaced the IAC with a OEM VP IAC (part# 3855185) and this has not remedied the situation. My next thought was that it would be the fuel pressure regulator. After a lot of research I have not been able to located a schematic which shows a fuel pressure regulator. The only thing I can find is the Pressure Regulator Cover (part# 3857397). Any suggestions would be greatly appreciated, because I am out of ideas as of right now.

Schematics referenced:

THROTTLE BODY INJECTION - 1998 Stern Drive 5.7 57FCPBYC | Crowley Marine

View parts diagrams and shop online for THROTTLE BODY INJECTION parts, 1998 Stern Drive 5.7 57FCPBYC. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.

www.crowleymarine.com

FUEL SYSTEM & INTAKE MANIFOLD -- TBI MODELS - 1998 Stern Drive 5.7 57FCPBYC | Crowley Marine

View parts diagrams and shop online for FUEL SYSTEM & INTAKE MANIFOLD -- TBI MODELS parts, 1998 Stern Drive 5.7 57FCPBYC. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.

www.crowleymarine.com

Thanks.

 

[alldodge]

Welcome
In most cases excess full causing black smoke is not the IAC. The GSi fuel pressure should be
Low side 5 psi +/- 3
High side 29 psi +/- 2

Your drive is called a Duo Prop, Mercruisers are called Bravo 3

I hope you have dumped the contents of the fuel filter into a clear container. This allows you to see if there is anything but clean gas

The TBI regulator is part of the TB and most can not be found for replacement in a parts house. They are GM TB so may be able to find one in that direction

Before changing anything else, check the pressure.

If pressure is good, look at the TB injectors. They should be pulsing and not dripping. Compare the good with the bad motor. If could be the injectors are the problem of the control of them. Would be a good idea to get them cleaned and flow tested by a good marine shop. Don't buy new ones from Ebay or Amazon

 

[TimoLKN]

Welcome
In most cases excess full causing black smoke is not the IAC. The GSi fuel pressure should be
Low side 5 psi +/- 3
High side 29 psi +/- 2

Your drive is called a Duo Prop, Mercruisers are called Bravo 3

I hope you have dumped the contents of the fuel filter into a clear container. This allows you to see if there is anything but clean gas

The TBI regulator is part of the TB and most can not be found for replacement in a parts house. They are GM TB so may be able to find one in that direction

Before changing anything else, check the pressure.

If pressure is good, look at the TB injectors. They should be pulsing and not dripping. Compare the good with the bad motor. If could be the injectors are the problem of the control of them. Would be a good idea to get them cleaned and flow tested by a good marine shop. Don't buy new ones from Ebay or Amazon

Thanks for the reply - I will check the pressure this week, and if those look good, then I will tear into the TB after that. I appreciate the response and I will keep this thread updated if I have any more questions.

 

[QBhoy]

First thing I’d be thinking is certainly around fuel not getting burned too. Although all ecu governed injection engines will run rich when cold..you’ve compared the visual and sensory symptoms with another identical engine.
If the two engines are fed from the same fuel source and not separate tanks..
This might make me head towards the ignition system first off plugs, distributor etc.

I might just do a compression check to rule out the unmentionable