Volvo Penta 5.7GSi Running Rich, Strong fuel smell


T

TimoC1

New member
Hey everyone,

I recently acquired a 1998 Forumla 280 SS with twin VP 5.7GSi TBI engines 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.

Thanks.
 
Have you taken the TBI unit apart? It almost seems like the injector is just wide open dumping fuel in the motor. If its been sitting, it would probably be a good idea to take it apart and have the injector professionally cleaned to make sure it is working right. Ultimately it will help make sure you are not running too rich or too lean when you do get it all back together.
 
Also, is this boat some sort of Frankenstein? Why does it have VP motors and Mercruiser drives? Which was correct for the boat?
 
gustaf said:
Have you taken the TBI unit apart? It almost seems like the injector is just wide open dumping fuel in the motor. If its been sitting, it would probably be a good idea to take it apart and have the injector professionally cleaned to make sure it is working right. Ultimately it will help make sure you are not running too rich or too lean when you do get it all back together.
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I have not taken the TBI unit apart yet, that is a possibility, I might look into that in the coming days and report back, Do you know if there is even a fuel pressure reg on these motors? I cannot seem to find it in the schematics.

gustaf said:
Also, is this boat some sort of Frankenstein? Why does it have VP motors and Mercruiser drives? Which was correct for the boat?
Click to expand...
The engines have about about 900 hours on them, as far as I am aware everything was original, but I am not sure. I know that one of the drives was replaced due to an insurance claim, but both of the drives are bravo 3s and from what I have seen online, it looks like the 1998 280SS came with bravo 3s with either a 5.7 or 6.2 configuration.
 
TimoC1 said:
I have not taken the TBI unit apart yet, that is a possibility, I might look into that in the coming days and report back, Do you know if there is even a fuel pressure reg on these motors? I cannot seem to find it in the schematics.


The engines have about about 900 hours on them, as far as I am aware everything was original, but I am not sure. I know that one of the drives was replaced due to an insurance claim, but both of the drives are bravo 3s and from what I have seen online, it looks like the 1998 280SS came with bravo 3s with either a 5.7 or 6.2 configuration.
Click to expand...
My fault, it's a DuoProp.
 
What I posted on iBoats
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
 
AllDodge said:
What I posted on iBoats
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
Click to expand...
Yup - I saw your reply. Thanks for the help AllDodge. I really appreciate it.
 
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