Merc 898 PCV system?

[Boomyal]

I assume the Chev motor, in this package, had a PCV valve inserted in one of the valve covers. Where did the hose terminate for it's vacumm source? Unlike the 888 (Ford) which had the PCV valve in the rear of the right valve cover, terminating at a fitting in the carb spacer, the Chev does not seem to share that arraingment.

In fact, the 898, had two hoses. one from each valve cover, connected to the flame arrestor. Neither connection at the valve cover had a PCV valve in it.

 

[Don S]

Re: Merc 898 PCV system?

Unlike Fords, 898's (Chevy 305) didn't use PCV valves.
Also, Mercs are different than OMC's.
Don't try to compare one to the other, it'll do nothing but make you crazy ........... er. 8)
To find out for sure you need a serial number or at minimum a year for your particular 898, then check the parts list for that engine.

Doug Russell has a parts catalog of all the Merc numbers and part discriptions.

 

[Boomyal]

Re: Merc 898 PCV system?

Don, we've got two near identical 18.5' BeachCrafts sitting side by side. One is a 1978 898 with the Chev, the other is a 1976 888 with the Ford.

The 888 Ford is just like my beloved OMC Ford in that it has the PCV valve inserted in the right rear rocker cover and hosed over to the fitting in the carb base.

The 898 Chev has two hoses emenating from hollow fittings in each of the valve covers and terminating at two fittings rivited to the flame arrestor. No PCV valves and no vacuum source to scavange the crankcase.

Are you saying that that is the way it was meant to be with the Chev?

I did look at the site you gave and it showed only one hose going to the spark arrester for the years '76 to '79.

 

[Reel Poor]

Re: Merc 898 PCV system?

It's plumed correct Boom. No PCV valve.

 

[Boomyal]

Re: Merc 898 PCV system?

It's plumed correct Boom. No PCV valve.

Well it does now RP. i pulled the hex plug out of the left side of the intake, right below the carb base, screwed in a pcv valve and plumbed it over to the hole in the front left valve cover. I left the hose, from the right rear valve cover to spark arrestor as a vent. The Ford has a vented oil fill cap, whereas the Chebby has solid unvented lids.

That's crazy, no late model motors want to run without a pcv valve. It keeps too much positive pressure in the crankcase. A no-no.

 

[Don S]

Re: Merc 898 PCV system?

I did look at the site you gave and it showed only one hose going to the spark arrester for the years '76 to '79.

Don't just look at the pictures in any parts catalog, look at the parts list and look at the quantities. 2 Connectores, 2 hoses, Only one shown.

Again, Chevy is not done the same as the Fords, even if they both say Mercruiser on them.

 

[Don S]

Re: Merc 898 PCV system?

Looks like we were typing at the same time.

My guess is you need to plumb the 898 any way that makes you happy. Doesn't matter what Merc had in mind. Do it your way and quit worring about what others (including Merc) say it should be.

 

[Boomyal]

Re: Merc 898 PCV system?

Looks like we were typing at the same time.

My guess is you need to plumb the 898 any way that makes you happy. Doesn't matter what Merc had in mind. Do it your way and quit worring about what others (including Merc) say it should be.

Thanks Don. Didn't intend to be impertinent. I just thought it would be good to ask even if after I made the fateful modification. It's an old boat and who was to know whether someone had made changes along the way. It just didn't seem right that the motor (car or boat) didn't have a PCV valve.

 

[lilmandavis]

Re: Merc 898 PCV system?

the thing is there isnt any vacum circuts so there isnt really any need for a pcv is there?ive seen em blow dipsticks out on some that have them installed. take it out- no dipstick rocket!

 

[fendersfender]

Re: Merc 898 PCV system?

I'm confused...Why insist on a pcv valve??? Why not leave it in stock form. Why mess with something thats not broke?????

 

[Boomyal]

Re: Merc 898 PCV system?

Why insist on a pcv valve??? [colour=red]Thought all motors needed them.[/colour] Why not leave it in stock form. [colour=red]Didn't know it was stock.[/colour] Why mess with something thats not broke????? [colour=red]Considering it's age and unknown number of owners, didn't know that it had not been altered.[/colour]

 

[KaGee]

Re: Merc 898 PCV system?

My Chevy is the same Boomer... No PCV... just the two hoses to the spark arrestor. The fumes get sucked back into the carb.

In fact, the only vacuum line is at the base of the carb for the choke pull-off.

 

[muc]

Re: Merc 898 PCV system?

If your going to leave the PCV in, you might want to rejet your carb, might be a little lean with the vacuum leak that was added. Good luck muc

 

[Boomyal]

Re: Merc 898 PCV system?

If your going to leave the PCV in, you might want to rejet your carb, might be a little lean with the vacuum leak that was added. Good luck muc

Thanks muc. This was in the works anyway. Not necessarily due to the pcv valve but because this motor is a 9.5:1 compression 283 bored to 292 with a slightly radical cam. When my friend got the '78 Beachcraft 898, the 305 was busted wide open due to the previous owners failure to winterize.

This motor originally was used, by my friend, in his butt buster boat. He sold that and put the motor in his Model A. When he transfered it to the beachcraft, he stripped off the 4 bbl carb and mani and put all the pieces from the 898 on it. He figured that the Rochester needed rejetting anyway. That ity bitty carb on a motor that had been running a 4bbl.

 

[Boomyal]

Re: Merc 898 PCV system?

The fumes get sucked back into the carb.

Well after a fashion KaGee. More accurately the fumes get wafted into the sid of the spark arrestor. There ain't much suction there to really scavange the crankcase and keep it in a negative pressure state like it should oughta be.

But then I never had much faith in Chebby engineering. My '94 Suburban is a classic example of what I mean.

 

[calwldlif]

Re: Merc 898 PCV system?

I thought (oops I did it again)
PCV was in response to smog
requiements? NO?

 

[Boomyal]

Re: Merc 898 PCV system?

Yes and no. The real old cars had road draft tubes. They did two things, one good, (for the engine) one bad.(for smog) They did vent the crankcase(good) but to atmosphere (bad).

The one thing they did do that the Merc set up does not is (note; road draft) they actually sucked blowby (positive pressure) out of the crankcase via the wind blowing by the tip of the tube, leaving the crankcase in a negative pressure environment. (desireable) In effect they mimiced what the later pcv valve, properly hooked to an engine vacuum source, did.

Running a couple of hoses out of the valve covers and terminating them a 1/8-1/4" away from the the 21" circumference of the spark arrestor, inside a closed engine compartment, hardly qualifies as a suction source.

 

[KaGee]

Re: Merc 898 PCV system?

Every one of that vintage OMC I've seen with the Chevy, are all done with the no PCV thing. It's not just a Merc thing.

 

[Boomyal]

Re: Merc 898 PCV system?

Every one of that vintage OMC I've seen with the Chevy, are all done with the no PCV thing. It's not just a Merc thing.

That's ok KaGee, I understand. GM was 10 years behind Ford in making wide use of sequential Mulitport Fuel Injection too.:% Then when they finally did, they acted like they invented it.

I could also flash my headlights with the turn indicater stalk in my '88 Mercury, can't do it in my '94 Suburban.