Mercruiser 7.4 problem

cheesegrits

Petty Officer 3rd Class
Joined
Jun 25, 2009
Messages
77
We were out on a friends Searay 370 yesterday and noticed that the port engine was putting out a good amount of black smoke. When we stopped to check it out the motor was also putting out some blue smoke. It doesn't idle or seem to run any different than the starboard one (or at least not enough to notice it). I do understand the black smoke is probably from running rich but the blue smoke is more of a concern. Both motors are 1996 EFI MPI hooked up to what seems to be a v drive system. I am more familiar with outboards than these big boat motors and all the complicated systems that are inherent with these powerplants. Any help or opinions with this will be greatly appreciated! My idea on the blue smoke is it could be valve guides or rings, other than that i am at a loss. With them being injected my thinking is they could be scanned to see if there are any codes. Thanks in advance!!!!
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
Re: Mercruiser 7.4 problem

We were out on a friends Searay 370 yesterday and noticed that the port engine was putting out a good amount of black smoke. When we stopped to check it out the motor was also putting out some blue smoke. It doesn't idle or seem to run any different than the starboard one (or at least not enough to notice it). I do understand the black smoke is probably from running rich but the blue smoke is more of a concern. Both motors are 1996 EFI MPI hooked up to what seems to be a v drive system. I am more familiar with outboards than these big boat motors and all the complicated systems that are inherent with these powerplants. Any help or opinions with this will be greatly appreciated! My idea on the blue smoke is it could be valve guides or rings, other than that i am at a loss. With them being injected my thinking is they could be scanned to see if there are any codes. Thanks in advance!!!!

Ayuh,.... A compression, 'n leak down test would tell 'im of any problems,....

Spark plug color while yer doin' the test, would also give alota hints to the problem,...
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Mercruiser 7.4 problem

Check your oil while you're at it! Just for peace of mind.
 

cheesegrits

Petty Officer 3rd Class
Joined
Jun 25, 2009
Messages
77
Re: Mercruiser 7.4 problem

Thanks for the replies guys!!!!

What do you think a mobile tech should charge for this. I am getting too old to crawl around these behemoths!

The oil looked fine!
 
Top