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V6 overheating at low rpm

"Troy, I am going to check the

"Troy, I am going to check the temperature of the water tonight out of the hub and get back to you on that.I am also going to install a clear hose (just to check)like Joe said to see if there are any bubbles in flow.The more we talk about it, the more that it seems that it is one of those things you mentioned in your last post."
 
"Keep that camera handy too, R

"Keep that camera handy too, Rich, I would imagine that some pictures of what is going on would be really handy. Given the recent questions about the water tube in the stern drive, I think it would be useful, if you crack the drive open again, to take pictures of the internals including the water tube."
 
"Rich,
I tried to post anoth

"Rich,
I tried to post another response but it did not get posted. However. I think the problem lies within the gaskets you installed on the exhaust manoifolds.If your boat is a closed water systen(fresh water cooled then the gaskets that are used on the manifold to the elbow (riser) are the ones with the four (4) slots. If the boat is raw water cooled the gaskets are the one with the two(2) slots and the two(2) holes in them. You cant make a mistake and install the ones with the little holes they ony fit one way. If the boat has riser blocks then the bottom gasket is the one with the four slots,The upper gasket has the one with the 2 slots and the two (2) little holes. I dont think that your boat has riser blocks? ( A 3" spacer that is placed ontop of the exhaust manifold.) The gasket with the four slots will not alow the water to remain in the block long enough to cool the engine."
 
"I did some readings with the

"I did some readings with the infrared gun again and they were basically telling me that the engine was heating up before the thermostat was.
2 minutes into running; inlet to stat hose temp.-67, inlet to circ. pump- 84, all 4 other hoses on t-stat -74,at this time temp gauge read 150. top of engine under t-stat-123. 4 minutes into running engine at idle; inlet to t-stat-71, inlet to circ. pump- 102, middle hoses to ehaust elbows-77, rear hoses from thermostat- 76, top of engine-142 gauge read 170.
I couldn't get a clear hose big enough to see about air in flow, but what told me that the problem is outside the boat, is that the water is COLD coming out of the exhaust hub. even when engine is hot. A leak is going on big time. It looks like most of it is just pouring out instead of going in.
p.s to Joe, the proper gaskets are installed at the exhaust elbows and t-stat housing. I don't have a closed cooling system.
Hopefully when I pull the outdrive again, I'll find the problem. Something tells me that the lower gearcase isn't connecting good with the upper drive housing."
 
""Something tells me that

""Something tells me that the lower gearcase isn't connecting good with the upper drive housing."

I agree, pull the lower unit off and see what the heck going on in there."
 
"I'm almost ready to say U

"I'm almost ready to say Uncle...
I dropped the lower unit again and took apart and reassembled the impeller pump housing. That all looked good. My only concern was this.. Why is the water pump housing so watertight with the gaskets and all ,when the riser pipe that goes up to the outdrive just sticks into it with friction? I don't know if this is normal or if this part is broken, but there is a piece of copper tubing that I can remove from the inlet port at the bottom of the upper drive.This piece is about 8inches long. all it does is press in. It almost looks like it is broken. The housing port also has some hard carbon on it like it got hot at one time. So does this pipe just press into the both the waterpump housing and the upper gearcase with just friction? That just seems to me that it would leak like crazy..Cold water still pours out the prop hub but only when the engine is running. It stops just as soon as I shut it down.I took some pics but don't have my usb jack with me today.I think that it is leaking right at white sleeve that on the impeller housing."
 
"I know it looks a little hoki

"I know it looks a little hokie, but when the lower and upper units come together, the tube from the upper slips into the sleeve, then into the coupling and seals in the o-rings in the coupling. So when the two are together, it should be a pretty snug fit. There should be a seal between the water tube and where it slips into the upper unit, that should be pretty snug too.

I wish you wouldn't have put the lower unit back on so quickly... I'm wondering if you could hook up the garden hose directly to the water tube going into the upper unit, disconnect the inlet hose to the T-stat housing, and see if you get full flow from outside the boat to inside the boat.
It appears that somewhere in the outdrive water is leaving the water passage and entering the exaust area. Maybe this will show you where."
 
"That's what I'll do.

"That's what I'll do. I didn't see a seal in the upper drive port housing .When I drop the lower unit again, I'll also remove that port housing and check it out. It really doesn't take long to do it. Troy, do you have any schematic on that upper water tube port? Thanks"
 
"Here's what I got. You ca

"Here's what I got. You can also see exploded view diagrams on www.mercruiserparts.com

<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">
[url=""][b]Upper Unit.pdf[/b][/url] (70.2 k)</td></tr></table></center><center><table border=1><tr><td>[img]http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">
[url=""][b]Lower Unit.pdf[/b][/url] (100.0 k)</td></tr></table></center>"
 
"Rich,
Are you saying that

"Rich,
Are you saying that the rubber gromit is missing from the upper water tube assembly?, if so you will not have a complete seal. If the upper portion of the water tube assembly is melted, then you will leak water and not deliver the correct amount to the engine. The entire kit cost about $16.00, it can be difficult to change.However to answer your question it is held in place by the rubber gromit that is shown in troys upper unit diagram. Read this next passage taken from Sterndrives.com
Check the Water Pocket Cover

The copper water tube fits up into the "Water Pocket".
The water pocket is held in place with four stainless bolts.
There is a gasket between the water pocket cover and the housing.
If the gasket is leaking, the engine will run hot.
The gasket tends to leak after a few years, especially in salt water units.
Take a rubber hose and clamp it to the copper tube.
Hold your hand tightly over the front water passage hole to plug the
passage and blow through the hose. There should be no leakage.
If you suspect a leak, pour a little soapy water around the water pocket and blow.
If you see bubbles around the gasket area, you will have to remove the water pocket
and replace the gasket.
Hope this helps"
 
"Thanks Joe and Troy, This sho

"Thanks Joe and Troy, This should help me find out where this water is leaking at.I have another question, How come that the black rubber washer (centrifugal something it is called) slides down the lower gearcase driveshaft OUTSIDE of the impeller housing. It looks like it should fit iside of the housing .What exactly does this do?"
 
"That one should be pushed suc

"That one should be pushed such that the lip is inside the housing...meaning half-in, half-out."
 
"It's the centrifugal slin

"It's the centrifugal slinger. I didn't see a lip on it Daniel, It looks like a thick flat rubber washer to me. It actually fits good in the pocket on top of the impeller housing but it shows the placement to be on top."
 
"Right, but isn't there a

"Right, but isn't there a v-shaped groove around the circumference of it? The bottom of the "v" should be lined up with the edge of the impeller housing, so that it's half-in, half out of the housing.

I thought that the purpose of it was to keep water from spewing out of the housing where the drive shaft enters. If that's not installed correctly, I would guess that a lot of water would not be making it up the water tube from the impeller...it would just spew out of the top of the housing."
 
"Rich,
The centrifugal sling

"Rich,
The centrifugal slinger helps seal the pump.
1. It keeps the water pump primed.
2. It deflects the spray away from the upper seals in the drive.
It sits on top of the water pump assembly, not inside it.
You can use the water pump with out it, but it is not advised."
 
"Thanks Knowing why , helps m

"Thanks Knowing why , helps me to better understand the dynamics and really ties things together. Now I really know what to look for and how to test for water flow/leakage.."
 
"The impeller kit should have

"The impeller kit should have come with a little plastic "tool" (looks like a washer with about 1/4 to 3/8" lip on the outer edge) that you use to push the slinger dwon the shaft and on top of the housing with just enough tension to keep it from mangling itself. Like Joe said, it does not, nor does any part of it go inside the housing."
 
"Rich,
If you are going to

"Rich,
If you are going to remove the drive, take a used 5/8" garden hose and cut off one end. Put the cut end into the bell housing where the alpha 1 gen 1 drive delivers water to the engine, make sure that it is a snug fit. Turn on the water and notice how it exits the two exhaust ports. You can now start the engine,( make sure the hose stay in the water delivary part of the bel housing.)If the engine over heats at this point then you know that the problem lies within the engine and not the drive. If the engine remaims cool then the problem lies in the drive. There is a tool that mercruiser sells that bolts on the bell housing does exactly this so that you can winterize and/or flush the engine with the drive off.Look at this cite,
http://www.mercstuff.com/page02.htm
The tool is at the bottom left part of the page. Dont give up, I am sure that you will solve the problem."
 
"I removed the lower gearcase

"I removed the lower gearcase and first checked out that rubber centrifugal slinger. The one that I had on there was flat with no lip, but I found another one in a new impeller pump kit (the guy I bought the boat from had some extra parts)and this one did have the small lip that Daniel mentioned..I put that one on but pressed it down as best I could. The impeller kit originally was installed last summer by a "boat mechanic", therefore I don't have that tool Troy talked about.
I removed the water pock housing up in the upper gearcase and it looked like it was partly melted from getting hot.It looked like s--t. I'll try to send a pic. what looks like an inner seal still looked intact, but I'm not sure how good the water pipe fits in it. it goes in but somewhat loosely.
I'm ordering one today, but in the meantime, I will do what Joe said and run some water directly into the engine. Also when I do install the new water pocket, I will put water on through that and see what happens.
Thanks again to all and sorry that this is a long troubleshoot."
 
"No worries Rich, hopefully th

"No worries Rich, hopefully that water pocket is the smoking gun.

Not having the 'tool' for the slinger is no big deal, just don't smash thing on top of the housing too tight. A loose fit with the bottom of the lip contacting the housing with light pressure is all it needs. The manual doesn't specify it but, a little smear of grease will help make it last until the next impeller change.

I'm glad Joe jumped on board when he did, up until then I was under the assumption that your drive was a Gen II... been so long since I read the first post, and we spent the first 30 or so posts looking at the engine, I forgot the year.

We may have a record for length of thread going on here... Andrew?"
 
"Rich,
If the water pocket

"Rich,
If the water pocket assembly was partially melted, then the drive was NOT DELIVERING the required amount of water to the engine.the "inner seal" that you talk about is a rubber o sleve with a nipple on it. the nipple portion sits in a little hole in the water pocket assembly. However, this will be already installed in the new kit. If you need help re- installing the drive upper and lower you can read this: http://www.outdriveshop.com/replace_alpha_one_waterpump.html"
 
"Thanks guys.Here I go..hopefu

"Thanks guys.Here I go..hopefully for the last time.It'll be a few days before I get the parts . Until then,I'll do the water test with the hose.I do need some good advice on the best way to reclamp the bellows in back of gimbal housing. I had a bit-h of a time reconnecting them last time. Do I need to get that bellows tool that spreads them ? Or do I do the connection to the outdrive first, and then to the transom? I know that you need to be part magician to do this but I just need to know the least difficult way to go about it.P.S.sorry about all the questions,Hopefully I'll be out of your guys hair soon."
 
"Dont' forget, Rich, that

"Dont' forget, Rich, that there's other people (like me) benefiting from this discussion! Here's a toast for speedy delivery of your parts and a solution to your problem...."
 
"Wich bellow, the gimbal gerin

"Wich bellow, the gimbal gering bellows or the exhaust bellows. If you are re- using the currebnt exhaust bellows, then you do not need the tool to install it. As for the gimbal bering bellows, you must install the bellows on the gimbal housing first. I have included a cite that will tell you how it is done. Read the section from "Good Morning"
http://www.sterndrives.com/replace_alphaone_bellows.html
You will also need to readjust the trim sending units read this
http://www.sterndrives.com/replacing_trim_senders.html"
 
Both Bellows. I removed both f

Both Bellows. I removed both from the gimbal housing when I changed the water hose last time.I'm just not sure if they are on fully to the back of the housing..I just want to do it over again right with the proper tools for my own piece of mind..Cheers
 
"Good morning, When I remove t

"Good morning, When I remove the waterpocket, It looked like someone took a torch to it. I have pics to send but I am not having good luck. If you can, Please send me some tips on how to send and I'll forward you guys the pics. I tried twice but it tells me that the file is too large.
The owner of the place where I quit bringing my boat to said that this is from running the boat dry. I know better than that. But he always had a habit of covering up shoddy work.
You gotta see this.."
 
Shrink the size of the picture

Shrink the size of the picture using Photo Editor or the like (whatever software came with your camera). You could also reduce the resolution and size of the picture in your camera's settings.
 
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