NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

[vleasum]

NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Please see authors last post.

Well, bought a Osco intake/exhaust Manifold and Riser for my I6 250CID Mercruiser pre-alpha stern drive.

I have read many posts on this site, and appreciate all the information I have learned.

My questions are as follows:

Since I am changing out the Intake manifold as well as the exhaust manifold, will I need to adjust the Carb?

Should I use a "lil dab will do ya" of permatex on the Manifold/Riser connection?

Osco instructions say to use "locktite on the manifold bolts, I am planning on using the "medium strength" on the bolts. What do you think?

I was wondering about using "plumbers tape/pipe dope" on the drain plugs, thoughts?

What about test running this thing in the water? Do I need to pour water in the manifold prior to startup?

Any thoughts would be appreciated.

thanks.
-V

 

[Haut Medoc]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Well, bought a Osco intake/exhaust Manifold and Riser for my I6 250CID Mercruiser pre-alpha stern drive.

I have read many posts on this site, and appreciate all the information I have learned.

My questions are as follows:

Since I am changing out the Intake manifold as well as the exhaust manifold, will I need to adjust the Carb?
MAYBE.....
Should I use a "lil dab will do ya" of permatex on the Manifold/Riser connection?

Osco instructions say to use "locktite on the manifold bolts, I am planning on using the "medium strength" on the bolts. What do you think?
Should be OK.....
I was wondering about using "plumbers tape/pipe dope" on the drain plugs, thought
Permatex aviation grade sealant.......
What about test running this thing in the water? Do I need to pour water in the manifold prior to startup?
NO......
Any thoughts would be appreciated.

thanks.
-V

Good Luck!.....

 

[Fishermark]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

You shouldn't have to mess with the carb adjustment.

You should however do the recommended change for the water flow through the manifold. Here is a diagram of what I am talking about:

Here's how I did it on my father's boat:

 

[vleasum]

Update.

Update.

Got the new osco manifold installed. No problems. Big casting. got it all calibrated elbow torqued to 50ft lbs.

Will install carb and linkage this afternoon. Hope to get this thing splashed on thursday afternoon/night for a test.

Need to get a steel brake line and bend it up to make the choke heat tube. Not sure what I am gonna do if that doesnt work, hole is in different location than oem location.

Otherwise, looking good.

Thanks for all the help, I did not reroute per the diragram, since this is a different design. Thank you very much for the diagram. Very informative.

 

[vleasum]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Alrighty, got the manifold hooked up.

Everything worked great. engine started right up. No carb adjustment.

Manifold ran hot, but the riser was cool.(backwards from previous symptom.)

Ran the motor with thermostat in and Thermostat out.(No change)

Checked the impeller. Impeller was due for a change (according to how it looked.)

Plastic base was partially melted. Seems that previous mechanic didn't do a complete job on the impeller replacement. Additionally, the stainless steel base was scored. Actually the base melted enough to partially cover the discharge ports of the pump.

I have purchased the new "upper" impeller kit (with the housing, etc) Additionally, I have ordered a new base plate. (plastic base).

I have changed all the hoses on the motor last fall (because they were 30 yerars old.)

I am planning to back flush this system tomorrow to see if i can recover an pieces of previous empellers.

In summary I have replaced/will replace the following:
hoses (inside doghouse)
Exhaust manifold and riser.
Bellows from riser to lower unit.
Impeller, impeller housing, lower plastic plate, stainless steel plate inside housing.
Thermostat.

I will also back flush the raw water cooling hose.

Anything I missed?

Thanks for your response.

 

[Fishermark]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Sounds like a good plan to me.
When you say the manifold is now hot... how hot is hot? It might be a good idea to get an infrared gun and check. But I believe your water pump replacement will solve your problems.

I'm also curious about this statement:

I did not reroute per the diragram, since this is a different design.

I too used an Osco manifold and elbow - how is your's different? All you have to do is replace the blank end cap with a cap that has the nipple for the hose.

 

[vleasum]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Based on the picture you posted, the manifold that you purchased looks like a OEM style manifold. The manifold that I purchased was of an Osco design.

I sure hope that the impeller fixes the water problem.

Funny thing is now my manifold is smokin' (literally) hot, but the riser and engine stayed cool.

I think that the thermostat also plays into it too.

I really appreciated the pictures and diagrams.

 

[Fishermark]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Based on the picture you posted, the manifold that you purchased looks like a OEM style manifold. The manifold that I purchased was of an Osco design.

Not to beat a dead horse... but Osco is a brand, not a design. You need the right manifold for your engine - whatever the brand is - Osco, Barr, whatever. The manifold pictured above is an Osco brand manifold for the inline six 250 engine.

Now maybe there is a design difference and option that I am not aware of, that's very possible. Is it also possible you have the wrong manifold?

 

[vleasum]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

No, the manifold is specific to the motor, but Osco used to manufacture a "log style manifold" that looked like the original mercuriser.

The manifold that I purchased is of a little different design than the log style. this thing is more like a square box. The manifold I purchase actually has an adapter that turns the riser back towards the bellows so it lines up.

Someone said that mercury actually bought this style as a warranty fix for the original style until they came up with the fix that you diagrammed.

 

[Fishermark]

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Re: Swapping out "exhaust" manifold on my I6 250CID Mercruiser pre-alpha stern drive.

Thanks for the info on the manifold.

I saw your other thread, and noticed you have directed people back here. (Although, as one poster mentions, most will not know where "here" is ).

Anyway, take care of the impeller and water pump issue - back flushing for any missing pieces as you mention. See if that helps.

Let us know how it goes. (It avoids confusion keeping all the related issues in one post. If you feel it has gone too long with no response, just bump it back to the top).

 

[vleasum]

Now this is starting to P*ss me off!

Now this is starting to P*ss me off!

Alrighty. Replaced impeller re-installed lower stern drive. Also replaced t-stat and t-stat gasket. Did backflush.

Started motor on muffs, worked water pumped great from the lower unit to the housing. hose from lower unit was solid, cold and had a lot of pressure.
Manifold still got too hot.

Took hose off end of exhaust manifold and restarted motor. Got good water flow from hose. (my opinion)

Made the following observations:
-Exhaust Manifold gets hot while engine is running, but cools almost immediately? Why?
-When I removed the hose from the manifold, the manifold was full of water.
-When I pinched the hose that runs from my t-stat housing to the manifold, it felt like it had a lot of bubbles.
-I saw what I thought was good flow from the lower unit through the prop hub. Had a spray of water through idle ports. The water through the prop was probably 80-90 degrees F.
-The riser remained cool.
-Engine water gallery is very clean(my opinion.)
-Raw Water cooled. Run Primarily on Lake Michigan. (40-65 deg F water)
I removed the circulating pump?? Not sure what a bad one looks like.. the impellers are intact. This is the type that fits into the block.

Should I remove the T-Stat housing? What would I be looking for there?


My guess right now is that the plugged up riser hid a multitude of problems with the cooling system, once I fixed the manifold/riser issue. The Others reared their ughly heads.

PLEASE HELP!!!!

 

[Bondo]

Re: Now this is starting to P*ss me off!

Re: Now this is starting to P*ss me off!

PLEASE HELP!!!!

Ayuh,.....

Did you do the Revsere Flow that Mark pointed out in his picture,..??

At this point,...
I think a Picture might Help,...
Seeing that Nobody has a clue as to what this Special Design Manifold looks like.....

With the motor Running,.....
Remove the hose that feeds the manifold,..... Is there Good Flow....??

Did you Inspect the cooling jacket of the New manifold to see if it's free of casting slag,+ flash pieces of cast iron,..??

 

[vleasum]

Re: Now this is starting to P*ss me off!

Re: Now this is starting to P*ss me off!

With the motor Running,.....
Remove the hose that feeds the manifold,..... Is there Good Flow....??

Yes, I have good flow. Appeared to be bubbles in water in flow.

The thing I go back to is... The bubbles in the manifold when I took off the hose to check it. seemed like a lot of air trapped.

What i am going to do now... "install vinyl tube" on the connection from T-stat to manifold. I am also going to run a garden hose straight to the exhaust manifold.
My thought is that if I have an issue with flow, running it directly on garden hose will keep the manifold cool.

I will post some pictures of the manifold.

 

[vleasum]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Well, I took apart the exhaust manifold.(end cap.) found water and a little flash rust in the exhaust manifold! Removed Riser and found water at the apex of the weater elbow.

Additionally, when I drained the riser prior to removal, the water that came out was black like it had exhaust run through it.

I case you were wondering, this is really beginning to suck.

I guess that I will re-assemble the parts that I can reassemble and call Osco 1st thing Monday morning.

 

[CharlieB]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

What should be an obvious question, which end of the exhaust manifold is your inlet water supply line connected?

Water MUST circulate the LENGTH of the manifold, either front to back and exit up through the riser
or
back to front and a seperate hose to the riser.

If your inlet is on the rear and straight up and out the riser then it should be obvious that you have next to no water circulation throught the forward section of the manifold and it will superheat.

Post your pictures.

 

[vleasum]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

My exhaust manifold is connected the way it is supposed to be per the instructions.

My issue now is that the manifold has water where it is not supposed to have water.

 

[Fishermark]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

I wish I could hep... but I'm out of answers. As mentioned above - a few pictures would probably help clear things up. And, as you say, maybe a call to Osco is in order.

 

[vleasum]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Thanks everybody for the help. I got a hold of OSCO today and we discussed what we are going to do with the manifold. I am waiting to hear back from them....

 

[vleasum]

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Re: NEW PROBLEM!! OVERHEAT!! Swapping out "exhaust" manifold on my I6 165hpMercruiser

Well, spoke to a marine mechanic while he was checking the compression on my new boat (outboard).

I explained my issue with my osco manifold, and the description of the problem. He said, "are you sure that the head gasket is ok?" Sure I said, it didn't have a problem before.

He raised the ol' eyebrow, and I had that sinking feeling.

Went back to the boat, and sure enough, the #4 cylinder had a little build-up on the plug (ok, a lot) showing me that I had a little water in that cylinder!

I am going to pull the head tonight. I found a machine shop that will magnaflux, pressure test, and resurface it for $75. I don't want to test the head with a $30 head gasket (marine) and 2-3 hours of work.

Like my buddy said, "someone is going to get one h3ll of a nice boat when you are finished."

 

[vleasum]

Update....

Update....

Got the head installed, machine shop took .007.

Torqued her all down, looked great.

Gotta get the rocker arms torqued correctly.

I'll let you know how it goes.

Need a new intake/exhaust manifold.