Re: [OMC-Boats] delving into scaryland....

From: Lee Shuster <lks@...>
Date: Tue, 8 Sep 2009 09:00:10 -0600


One tool that you'll find invaluable is the illustrated OMC Parts
Catalog. Available FREE online at BRP-OMC or CROWLEYMARINE.COM. OR you
can but a REAL HARD COPY at BRP or look forever on eBay. I feel like a
broken record, but I get the idea few of us have these, by the nature
of a lot of the questions that crop up here.

Careful study of this "EXPLODED" diagram will revel (4) bolts holding
each cyl head to the block. It is a simple as your lawn mower, times 6
cylinders. With the OMC PARTS CATALOG it's like you have X_RAY vision!

New Parts for the 3.7 Litre or 225 cu in ODD_FIRE BUICK V6 are
relatively plentiful and easy to obtain including rebuilt short or
long blocks. Even the OMC log-style. exhaust manifolds are still
available, but they are expensive, see below)
Nothing particularly expensive or specialized, as GM and Jeep built
this engine for years. Just don't confuse it with it's 231 cu in
(3.8L) even-fire sister. Anything you might need for this engine is
available, if you carefully explain what you have and ask the right
sources. This was probably the second most popular GM engine that OMC
used after the 100-110-120-140 Chevy-II 4-banger.

If this were my project, I'd start by having getting help to remove
the stern leg. Then I'd carefully determine if there's room on your
boat to pull the engine and intermediate out as a unit to gain better
working access in a clean shop environment.
easy to stress (causing cracks) in the head mating flanges by lifting
on the manifolds, so DON'T DO iT!). This will cost you big money. If
it were mine, I'd carefully remove the exhaust manifolds, before
removing the heads, to reduce the weight and possibility of ruining
the manifolds.

And Bill's right, treat that motor to a nice valve job. They'll most
likely install modern hardened valve seats (for lead free gas).

The timing is right to get started on good off-season project. Also,
the fact that you mentioned a spark plug with NADA-gap is SIGNIFICANT.
That plug most likely has encountered MECHANICAL interference and will
PROBABLY be a clue as to where the SOURCE of your strange NOISE is.

BTW, what year/model is you boat? From you pictures, your Buick V6
appears to have been retrofitted from a 72-73 era OMC. Do you have a
serial number or model number off the engine tag? It's not all that
important, just curious.


On Sep 8, 2009, at 7:56 AM, BLDFW wrote:

> I've pulled a couple of engines apart to do a rebuild. The tube or
> bar is just holding the valve rocker arms in place. It rests on top
> of the rods and the springs. The springs hold the actual valves and
> are held in place by a snap ring that holds the little round 'cover'
> you see. You are safe to remove the bar and the rocker arms. They
> will either lift out with the bar or will just rest on the rods and
> valves and you can pluck them off one at a time.
> The heads, once unbolted, will have to be gently prided up to free
> them from the block and yes, they will be trashed so you will need a
> new gasket set. Since you have already gone this far, I would
> seriously recommend considering going the next logical step and
> sending the heads out for a valve job. Would be a shame to waste
> breaking the engine down this far and not doing that but then again,
> if it's not necessary, no sense in doing it either.
> Good luck and keep us posted!
> -Bill
> Dallas, TX
> 1970 Evinrude Explorer - 155 Buick V6 - OMC Sterndrive
> --- On Tue, 9/8/09, jd <jdood@...> wrote:
> From: jd <jdood@...>
> Subject: [OMC-Boats] delving into scaryland....
> To: "Evinrude & Johnson Boats of the 1960's and 70's" <omc-boats@...
> >
> Date: Tuesday, September 8, 2009, 12:30 AM
> right on the heels of getting my switch issue overwith, and having
> a fabulously smooth 30 min test at WOT right after the other day,
> I was ready for a real outing. but of course, not without a new
> issue to solve springing up. and not a pretty one. I was at the
> dock (fortunately) and had just got back from my test run. Was
> playing with idle trying to get it to go down to where it's supposed
> to (sticky cable issue i think). in the spirit of trying to learn
> what does what, i pulled off the spark arrester and started playing
> with the flapper inside the carb. a tiny little brass screw that
> partially held the flapper together was barely screwed in and sure
> enough dropped down into the black abyss of the carb, never to be
> seen again. I put stuff back together, started, no probs -
> smooth. started moving the red throttle lever back and forth.
> all of the sudden a clanking noise. however, coincidentally NOT
> the screw - a much bigger clanking noise, and only at low idle -
> often causing stalls. And in fact, i had heard this same noise
> 2-3 months ago during a start up. immediately shut it down. it
> never came back, and i forgot about it. so here it was again,
> this time a lot worse and causing engine to stall. a car mechanic
> guy happened to be at the dock, listened around the engine with
> me, sounded like it was coming from the port side, deep within
> somewhere. It's definitely the sound of a "metal piece" sort of
> bouncing and clanking around inside the engine. It's not a rattle
> type sound, more of a random clanking - like coins in a dryer.
> And it sounds big - not like a tiny brass screw, but a nut or
> something bigger. ugh.
> So long story short, he suggested i start with the valve covers and
> see it anything is loose. the remove the intake manifold. as
> you can see, have done both. jiggled a tiny little piece of
> solder (from a previous owner's attempt at repairing carb flapper)
> out of the IM, but no brass screw. So now I'm on to the only
> next place I can go, the cylinders. Pulled the plugs out,
> nothing unusual with them. One had NO gap whatsoever, but
> probably unrelated. time for new plugs regardless.
> So my questions are these: I'm about the pull off the cylinder
> heads. have never gone this far into any engine. and am flying
> somewhat blind. yes, i have all OMC 3 original manuals. yes,
> i've read them. they aren't much help. So excuse my ignorance
> beyond this point. But there's no way I am handing my boat off to
> another mechanic for another year. Gotta go it alone.....
> 1)As shown in the photo. there appear to be about 8 bolts holding
> the heads on. 4 inside, 4 down by plugs. but unscrewing those
> doesn't look like it will do much because all the valve stuff. So
> if i undo the 3 bolts holding that bar of levers, will it just
> come off easily and allow for the rest of the head to come off
> somehow, or will springs go flying everywhere? I don't wanna mess
> with valves if i can help it. just wanna get to the cylinders. So
> much easier on a lawn mower. Manual says remove heads WITH
> manifolds still attached. But can't get to a couple bolts cause
> manifold gasket is in the way. So i guess I'll be taking those
> off as part of this.
> 2) Will the head gaskets be trashed after this, or salvagable?
> Anyone know right off hang if they are they out there for sale, or
> one of those impossible to find way overpriced no longer made
> vintage parts? Yes I will poke around online, but just trying to
> get an idea....
> 3) After i get the heads off, I'm assuming I will be able to see
> the tops of the pistons. I'm not expecting much, but perhaps I'll
> find something obvious clanking around in one of the cylinders.
> perhaps a coin, or a wedding ring, or maybe the top half of a
> spark plug. probably not. So where is the next place deeper
> within that something could be clanking around? what's under the
> cylinders? Could the oil pump be making that noise? It wouldn't
> cause the stalling though.
> glad it's the end of the season.
> thanks for any help, Jeff D
> -----Inline Attachment Follows-----
> _______________________________________________
> OMC-Boats mailing list
> OMC-Boats@...
> _______________________________________________
> OMC-Boats mailing list
> OMC-Boats@...
Received on Tuesday, 8 September 2009

This archive was generated by hypermail 2.2.0 : Tuesday, 29 July 2014 EDT