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Mercruiser 7.4 inboard fuel in oil

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mstanaszak

New member
I have 1997 Mercruiser 7.4 that is getting fuel in the oil, raw fuel smell from exhaust but no sheen on the water.
Engine runs great, compression good, and mechanical fuel pump replaced, plugs, wires, cap, and rotor replaced.

Any ideas? Mechanics want to go straight for the injectors.
 
Yes people there is a mechanical lift pump in the fuel system. Learn up.

Uh, so I hope you aren't running this with the oil contaminated or else you'll be buying more than just a few external engine parts. If your injectors are clogging you need to find out why. It's better to just replace all of them with refurbished units than to try to fool with what's there. You can get them pretty cheap on eBay or from Rock Auto if you want a warranty and the ability to return them. Def check the filters and don't forget the one in the VST high pressure pump.
 
No, turned into a floating cottage as soon as I discovered the issue. It’s a new boat for me and I suppose injectors are the issue since it’s had little use over the past several years. So you recommend cleaning injectors and vst? Also probably dumb question, but
1. Why would it be running so well?
2. Why is the other engine not experiencing any symptoms?
 
mstanaszak said:
I have 1997 Mercruiser 7.4 that is getting fuel in the oil, raw fuel smell from exhaust but no sheen on the water.
Engine runs great, compression good, and mechanical fuel pump replaced, plugs, wires, cap, and rotor replaced.

Any ideas? Mechanics want to go straight for the injectors.
Click to expand...

Hi,
Did you ever find the cause of the fuel in oil?
I have the same issue with my 2000 7.4L 454 Horizon.
White smoke(more at idle) and fuel smelling exhaust.
Also oil is getting soaked in petrol.

Have tried everything including injectors and problem is not going away.

Reply will be much appreciated.

Thanks
 
o2batsea said:
Yes people there is a mechanical lift pump in the fuel system. Learn up.

Uh, so I hope you aren't running this with the oil contaminated or else you'll be buying more than just a few external engine parts. If your injectors are clogging you need to find out why. It's better to just replace all of them with refurbished units than to try to fool with what's there. You can get them pretty cheap on eBay or from Rock Auto if you want a warranty and the ability to return them. Def check the filters and don't forget the one in the VST high pressure pump.
Click to expand...

Hi,
Looking for help on the same issue-
Have a 2000 454 Horizon 7.4L

Only stbd engine came up with this issue.
White fuel smelling exhaust and also noticed/smelt fuel in oil.
Have replaced so many parts but issue isn't going away.
Replaced VST Diaphram+ HP pump I side VST+distributor assembly + spark plug and wires+MAP sensor+PCV Valve+ fuel pressure regularor on fuel rail+ Sea water pump impellr+all 8 injectors with aftermarker ones to see if that solves it.

Nothing solves it!
Slight white smoke in 3xhaust which smells 'fuely' and also fuel smelling oil persist.

Help wanted pls.
Thanks.
 
Ozcruiser said:
Hi,
Looking for help on the same issue-
Have a 2000 454 Horizon 7.4L

Only stbd engine came up with this issue.
White fuel smelling exhaust and also noticed/smelt fuel in oil.
Have replaced so many parts but issue isn't going away.
Replaced VST Diaphram+ HP pump I side VST+distributor assembly + spark plug and wires+MAP sensor+PCV Valve+ fuel pressure regularor on fuel rail+ Sea water pump impellr+all 8 injectors with aftermarker ones to see if that solves it.

Nothing solves it!
Slight white smoke in 3xhaust which smells 'fuely' and also fuel smelling oil persist.

Help wanted pls.
Thanks.
Click to expand...
Best to start a new thread with this issue so that there is a better "paper trail" for us to follow. I would look for stuck open valve since you seem to be getting raw fuel in the exhaust. A compression test and leak down test will pinpoint. Stop randomly throwing parts on there without firm data.
 
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