new owner of MPI 502 mag; serial number? puking oil?

[bbender785]

so last fall I traded my motocross trailer for a 1992 Rinker 236 Sport Cuddy. I've been on my in-laws' boat for the last 10 or so years, but now that my wife and I suddenly have two kids under 2 years, we realized it was time for our own. I ran it for 10 minutes before it was put away for the winter last year, so the "official" mayden voyage was Memorial weekend this year. Anyways, here are my questions.

1. would this have come with the MPI fuel injected 502 its equipped with? seems like some others i see of this year had 502's, but usually carbuerated.

2. i've found a couple merc service bulletins online stating where i can find the serial number on the engine, but i cannot locate it. closest i've come is a casting number on the rear of the block.

3. my main reason for coming here. this boat starts, idles, and motors along great... until you open it up full throttle, at which point it blows oil out of the intake all over the starboard side of the engine/compartment. first notion is massive blow-by, but i'm wondering (hoping?) it has something to do with the way the PCV system is set up. instead of having a PCV valve between one valve cover and the intake manifold, and another vent tube from the other valve cover to the flame arrestor, BOTH valve covers have a PCV valve on them (with different p/n's on each), and they are T'd together and running into the intake manifold.. leaving the flame arrestor port unused. i've been up and down the internet understanding the PCV system and looking at alternative setups and i haven't seen this particular one.

is there any chance thats my problem? is the vaccuum inside the intake manifold at full throttle pulling oil out of the pressurized crankcase?

- engine idling, there is lots of vaccuum at the valve covers when i pop a PCV out and put my finger over the hole
- oil level is on the low side (not overfilled)
- no water in oil
- both valve covers have baffles


i know the logical thing to do is start with a compression test, which i am doing this week, a well as an oil change.

thanks!!

-brandon

 

[alldodge]

:welcome: to iboats Brandon

You stated the boat has a carb, with a carb it is not an MPI. It may be a 502 but in 1992 I don't see a MPI in the mix. The serial number is un the plastic flame arrestor cover but it sounds like you don't have one. Look above the starter there should be a plate there. If you do have the casting number let us have it and we can look it up.

The PVC systems would not be causing excessive oil blow-by, the PVC setup is to control blow-by. ~~It does this by allowing the carb to suck the oil fumes back into the engine. I am assuming that the oil is coming out of the valve cover tube and with that your engine probably has some bad rings. You have the right first choice in doing a compression test.

 

[bbender785]

thanks for the welcome and response AllDodge! but i didn't state my boat has a carb.. it's definitely MPI. that's why i question the originallity of the engine in it, the boat being a '92 model year.

I know the current PCV setup isn't -causing- blowby persay, just thought maybe it was sucking oil since both are T'd together and running into the intake manifold, with no fresh air supply, creating a vaccuum in the crankcase when running WOT.

the info i've found online thus far says compression should be in the 140-150 range, no?

EDIT: as far as the serial number, i don't see said plate anywhere around there either; is it something stuck on the block or is it like an axle differential tag where its connected by a single bolt? that was the first place i looked, and after not finding it found the forementioned merc document about it being stamped onthe block. i'll look again.

 

[bbender785]

here is a pic of the PCV routing:

 

[bbender785]

top of intake manifold:

 

[scoflaw]

Sound like the PO was trying to take care of his blowby problem by adding the 2nd pcv. Problem is, at WOT there is no manifold vacuum and that's when the blowby rears it's ugly head

 

[alldodge]

I have the same engine in my Cruiser but my hoses do not have PVC valves in them there just open connections. The difference is my hose does not connect to the intake, it has a short piece of hose which sits just below the flame arrestor. See item 30 and 31 in the link below

http://www.mercruiserparts.com/Show...&bnbr=20&bdesc=CYLINDER+HEAD+AND+ROCKER+COVER

In the link above mine has another hose which connects to item 29 so both sides breath. I do get some build up under the arrestor so it needs to be cleaned every once in a while. So with oil being only all over the starboard side I take it, the oil is blowing out of the tube on that side? Guess you could plug the manifold connection and run straight fittings so anything that comes out would be pulled in as mine do, but looks like your arrestor has been removed. The 502 is known to use oil but yours is building up some higher then normal pressure in the crank case.

 

[bbender785]

Sound like the PO was trying to take care of his blowby problem by adding the 2nd pcv. Problem is, at WOT there is no manifold vacuum and that's when the blowby rears it's ugly head

that was my notion too. i thought i read that if the blowby is really that bad it will puff vapors out of the valve covers even at idle if the oil fill cap or pcv valve is pulled out, but its much the opposite, plenty of vaccuum.

 

[bbender785]

..So with oil being only all over the starboard side I take it, the oil is blowing out of the tube on that side? Guess you could plug the manifold connection and run straight fittings so anything that comes out would be pulled in as mine do, but looks like your arrestor has been removed. The 502 is known to use oil but yours is building up some higher then normal pressure in the crank case.

its actually coming out of the flame arrestor (which i have & use, but is removed in the pic i posted). i know its hard to really know until i get some compression/leakdown numbers, but in the meantime i'm theorizing. think i'm going to run a catch can setup regardless.

 

[scoflaw]

even at idle if the oil fill cap or pcv valve is pulled out, but its much the opposite, plenty of vaccuum.

Vacuum at the valve cover with pcv removed??

 

[bbender785]

Vacuum at the valve cover with pcv removed??

yes, it makes a solid "pshh" when i pull one out, and putting my finger over the hole i can feel the suction.

 

[bbender785]

..which i assume is a result of both valve covers being T'd & plumbed into the intake manifold. or perhaps a leaking intake gasket?

 

[scoflaw]

With nothing connected to the covers ,and vacuum, yes intake leak.

 

[bbender785]

i'll have to pull both lines off at the same time, havent done that.

 

[bbender785]

so i rerouted the starboard side to the flame arrestor and replaced that PCV valve with an elbow (basically set up like OE now). i've only been able to run it on the muffs in the driveway so far but now at idle i don't have any vaccuum, or on the conbtrary any "puffing" from the valve cover with the PCV valve pulled out. so i'd like to think if my blowby was real bad i'd have puffing going on.

planning on running the boat this saturday, we'll see what happens.

 

[alldodge]

Something doesn't make since; you have oil coming out of the arrestor from the valve cover hoses, but when the hose is removed from the cover you get a vacuum at the cover. If the bottom of the intake was cracked it could be sucking crank case gases in and may even cause a slight vacuum at the cover, but that would still be a long shot. Having enough vacuum to hear and feel I don't see the engine running at all. Now if it is pressure being pushed out of the cover, I could agree,

Now with no puffing as you mentioned, it's probably blow by and will show back up

 

[bbender785]

i was getting a vaccuum at the valve cover when both vent lines were T'd together and plumbed into the intake manifold; so at that point when i would remove one PCV valve, the other was still connected and the intake manifold was sucking the crankcase pressure out, which was the vaccum i felt at the open hole on the other valve cover(in my head anyways).

now that i ran the one valve cover to the flame arrestor with an elbow instead of a second PCV, if i remove the remaining PCV valve i don't have that suction anymore (which coincides with the above).

i get the feeling you follow me, just thought i would clarify in case otherwise.

i'm still assuming blowby at this point too. i'll figure it out one way or another.

 

[Fun Times]

Is your flame arrestor plastic or metal? sounds like and kind of looked like you would have had a plastic flame arrestor from the photo. Also for your fuel pump, do you have a fuel vapor separator tank near the rear of the engine or do you have a fuel cooler down under the port side motor mount? In 1997 Mercruiser started using plastic flame arrestor and closer to 98 they went to the cool fuel system. You will notice most of the serial number breaks in the link below. Between the two serial number breaks, It should help with finding most basic parts since you can't determine the year. Also a photo of your ECM and an over all photo of the engine may help tell a story as well. Sometimes you can find a serial number on top of the electrical box and a white sticker around the flywheel housing area. While you may find a few "test boats" from late 1992 with 502 EFI's in them, most of the 1993 + boats would have a 502 EFI in it as standard.

http://www.marinepowerservice.com/B...ear/1997/pickDrive/0F802350 THRU 0K999999.cfm

 

[bbender785]

Is your flame arrestor plastic or metal? sounds like and kind of looked like you would have had a plastic flame arrestor from the photo.

...In 1997 Mercruiser started using plastic flame arrestor

the housing is plastic. would that be a black and white indicator of a 97+ engine?

Also for your fuel pump, do you have a fuel vapor separator tank near the rear of the engine or do you have a fuel cooler down under the port side motor mount?

...and closer to 98 they went to the cool fuel system.

i'll have to check.

You will notice most of the serial number breaks in the link below. Between the two serial number breaks, It should help with finding most basic parts since you can't determine the year. Also a photo of your ECM and an over all photo of the engine may help tell a story as well. Sometimes you can find a serial number on top of the electrical box and a white sticker around the flywheel housing area. While you may find a few "test boats" from late 1992 with 502 EFI's in them, most of the 1993 + boats would have a 502 EFI in it as standard.

http://www.marinepowerservice.com/Bo...200K999999.cfm

i appreciate the info. i'll look into all of this and report back. have a good weekend!!

 

[bbender785]

i do know i have this seperator filter directly under the intake near the starboard engine mount:




EDIT: looks like both systems use the same setup. i'll look into it tomorrow morning.