Help determining what to replace?

[Lou C]

Well I’ve been working on my own engines since 1972 and have never seen that! One thing that might cause that is excessive blow by (worn piston rings/cyls/pistons) putting oil vapors into the hoses and as it cools it drips down into the flame arrestor and then the carb. Seems far fetched but for the life of me can’t figure how else the oil got there!

 

[QBhoy]

You’ve surely got a poorly sealing valve on that cylinder.

 

[Tyger23]

Well, let me say this in my best "Bones" voice:

Thanks for making me check the leak-down in the other cylinders, even if it did rip out my heart and stop on it.

They're all showing "moderate" leakage, and it's mostly out the crank case. Bad rings. Bad news.

Time for a new motor (and probably a new carb). At least now I know. Thanks for all the patience and help on this!

One thing that might cause that is excessive blow by (worn piston rings/cyls/pistons) putting oil vapors into the hoses and as it cools it drips down into the flame arrestor and then the carb

This is the only theory I can come up with. The port side crankcase breather is an open elbow and feeds straight into the arrestor. The "foam" gasket at the arrestor was quite oily. The starboard side breather routes through a PCV and into the intake manifold at the bottom of the carb.

I'm guessing that there's something else wrong with the motor as well, but it's just not worth spending any more time on it. Now I've got bigger fish to fry.

Side note: For what it's worth, I was having a booger of a time finding the "leak" source since the noise seemed to come from a very generalized area. So, being an old "audio" guy, I know mics are very susceptible to wind noise. I made a video recording while the leak-down test was running, and held the phone's microphone over the ports I have exposed (exhaust, thermostat, distributor, and intake). You can listen to the video below if you want. While the "intake" has a good bit of noise, I believe you're just hearing the wind noise blowing through the crank case. When I hover over the "distributor", you can clearly hear the "wisp" of wind. Maybe this helps someone who finds this later.

https://photos.app.goo.gl/j2fQ8LXkBNgKL5nK8

 

[Tyger23]

That stuff on ther rockers, it is corrosion?

My best guess right now is Stop Leak, Rislone, or something similar. If the PO was seeing a lot of oil like I was, then he likely tried some bad-idea home remedies they picked up at Wal-Mart. Ugh. Oh well, at least my bilge will get cleaned, and I'll actually be able to get to the grommet-clip holding in the trim sender and change that out. Positive thinking, right?

 

[Lou C]

another thought...if the inside of that engine is as free of corrosion as the exhaust, and you have a local machine shop you trust, it might be worth a rebuild...

 

[Tyger23]

This is probably a good core that a re-manufacturer would start with. But for me, I will make the assumption that it will still cost me ~2-3K in parts and labor before it's done. While it would be a labor of love, and I might end up keeping this block and do that later -- I'd prefer to get back out on the water asap, for roughly the same costs. Maybe I'm wrong, but that's my current opinion. Happy to be swayed .

 

[Scott Danforth]

is excessive blow by (worn piston rings/cyls/pistons) putting oil vapors into the hoses and as it cools it drips down into the flame arrestor and then the carb.

Winner Winner chicken Dinner.....

 

[Scott Danforth]

This is probably a good core that a re-manufacturer would start with. But for me, I will make the assumption that it will still cost me ~2-3K in parts and labor before it's done. While it would be a labor of love, and I might end up keeping this block and do that later -- I'd prefer to get back out on the water asap, for roughly the same costs. Maybe I'm wrong, but that's my current opinion. Happy to be swayed .

do the assembly work yourself, and call your local machine shop. total cost of a re-fresh with new pistons, rings, bearings and gaskets is about $1500. a complete new motor (new everything) is about $3k

If you want to go stroker, the stroker kit will add about $600 add $800 for forged bits and baubles.

 

[Lou C]

I’d pull the heads and look at the cooling passages. If they look as good as the exhaust; and you can find a good reliable machine shop it could be less trouble than ordering an engine unless you use a local dealer. For sure can see your thought process tho. It’s a Vortec you can still get new; and keep the old one for a project to do over the winter as a spare...

 

[Tyger23]

a complete new motor (new everything) is about $3k

Just curious - where do you get your engines? For low-man on the totem-pole Joe Blow like me, the cheapest I'm seeing for a re-manufactured marine Vortec long-block is $2K (at marineengines4less/center state engines). When you add shipping, gaskets, circulation pump, etc - I'm at almost $2500 for the reman.

I have seen where Rapido Marine sells their long-block for $1600, but it doesn't seem to include essentials like push rods, head gaskets, head bolts, timing cover, valve covers, harmonic balancer, etc. By the time all that gets added on, I'm up to the 2K I see above.

For a new engine, the cheapest I've seen is $2859 at marineengines4less or $3059 at Michigan Motorz. The latter includes circulation pump, etc. But by the time shipping is done, we're well past $3K.

If there's another source I haven't found - please let me know!

 

[Lou C]

and Michigan motors sells NEW for approx. 3000. Might be worth the difference.
https://www.michiganmotorz.com/vortec-base-marine-engine-1996-2016-p-283.html

 

[Scott Danforth]

I have covered it multiple times. New GMPP blocks and heads from Salee Chev or your local GM dealer. Rotating assemblies from Summit or Competition Products.

Do your own assembly work

Or Central states for GM marine crate motors (they take less of a fee than Michigan Motorz for the same GM crate motor

On a rebuild. You open a can of elbow grease. You pull the motor apart and inspect everything yourself. Then you work with you local machine shop and get the machine work done. You then assemble the motor yourself.

If you pay for teardown, cleaning and assembly, you are paying for 10-15 hours of labor at shop rate.

 

[Tyger23]

Just to keep up to date, in case anyone reads this later:

I took apart the carb and found just too many changes to remain comfortable with it. Size 76 jets (6 sizes over factory spec), the wrong power valve, etc. Along with the missing choke plate and automotive vent tube, I decided to scrap that carb. Who knows what other changes were made.

So, a new motor is on order, as well as a new carb. I'm upgrading to a 4bbl, as the costs were roughly the same. Brand new 4bbl Volvo Penta Holley from MarineEngine (NOS from a pre-vortec 4.3L), and longblock/manifold from MarineEngines4Less.

I know I'll probably need to adjust the 4BBL for the Vortec, but it should be able to get me going better than my old 2bbl.

B.O.A.T. is an appropriate acronym, right?

 

[Tyger23]

I wanted to dredge up this old thread to give a bit of closure. My son and I started taking apart the old motor as a "learning experience". Surprisingly, it looks pretty decent. That being said - I do think I found the smoking gun(s) on the reason(s) why this motor was behaving as such...

As noted before - the input valve on cylinder 4 was leaking. Although not visibly "tulip-ed", it was definitely heated (the valve was much whiter than others). That appears to be the case (although not to the same extreme) on cyl's 1 and 3 as well.

The overheat was obviously from a shredded impeller. How do I know? Well, I found bits of an old impeller stuck inside one of the starboard side head cooling passages. See the photo.

The oil that seems to be coming out of the intake manifold? Well - there was a significant amount of oil located on top of the cylinder 4 piston (the same one with the leaking intake valve). I don't know why the oil on top of cylinder 4 was there, but I'm assuming it's significant blow-by. From there, the oil would get shoved back up and through the leaking intake valve during the intake stroke.

Anyways - I'm always up for suggestions, but I was hoping this might help someone in the future.

 

[Tyger23]

More photos of the cylinder heads. You can see where 4 and 2 are "whiter" than the rest, but only 4 tested bad. No obvious tulip-ing from what I can see.