Mercruiser 6.2L MPI overheating

[blamtro]

My boat is in the garage so no water will be getting in there.

Its about any water that is in suspension with the drive lube when you drain it and moisture in the air that moves in when the lube drains. That moisture cause rust when sealed in with no new drive lube.

 

[tpenfield]

I'm going to drain the gear lube first, I was going to drain it today and let it sit for 24 hours to drain everything out and then in a few days I will take it apart and look for blockages.

If I drain the gear lube and just leave it empty while I work on it, is that going to cause a problem with the air getting inside the sterndrive?

I had a bad experience in leaving one of my outdrives empty (without gear oil) for a few months over the winter and in a partially heated garage. (maybe 50-60˚ F). When I went to service the outdrive in the spring it was locked up from the small amount of surface rust that had developed from the air in the drive. About $500 and quite a few labor hours later I was back in business, having replaced a bunch of the bearings in the outdrive

 

[platon20]

Update: I finally got the drive off and discovered why the engine was overheating.

The water inlet hose thru the sterndrive had a sizable crack right before it enters the transom, which reduced the amount of water flow thru the tube and thus starved the the engine of the water it needed to stay cooled.

Now that I've figured that out, I ran into another issue. One of the small screws that holds the trim sender on the gimbal ring is completely stuck. I've tried the following things to get it out, and none of them worked:

1. Tape trick
2. Rubber band trick
3. Penetrating oil
4. Impact driver
5. Using pliers to grab the head and rotate
6. Cut a slot thru the head with a dremel to get a flathead in there

The head of those tiny screws is EXTREMELY malleable, the metal is very weak and bends easily with just a regular screwdriver in it.

I'm not sure what to do next, I guess my other options are 1) try a screw removal/drill set, but I dont think they fit screws this small; or 2) take out the gimbal ring and completely replace it with a new one, which I'm sure is very cheap (/sarcasm)

Another thing I guess I need to do is replace the gear lube hose that runs from the transom thru the gimbal ring to the bell housing. All of the youtube videos said to just cut it, which seems absurd to me that you hsould have to destroy something just to get the bell housing off, but I did it so I need to fix that as well.

And finally, the trials of going thru all this made me realize what a poor design it is to use a thin malleable hose to run water all the way from the lower unit of the sterndrive thru the transom buried under a bunch of other machinery, and finally to the impeller housing.

I'm seriously thinking about putting in a thru hull water inlet hose that runs directly to the impeller. That way it's a very easy fix if there's some kind of blockage or leak that doesn't require me to spend hours to figure out where the issue is.

I know some people create a T joint that brings in the water from the sterndrive and a second hose that runs to the thru hull, but I'd rather just abandon the sterndrive water pickup and put one big hose with a seacock valse and sea water strainer. I figure I can greatly increase the flow of water that way instead of using Mercruiser's small flimsy collapsible rubber hoses that they use in the sterndrive.

 

[Bt Doctur]

are the inlet and outlet hoses correct?
Could you be sucking air?

 

[Lou C]

This is mainly a Merc issue that is exacerbated by having the impeller up on the engine. It can also happen on Volvos and Cobras because there is a plastic water nipple in the pivot housing (bell housing) that can crack if the boat is not properly winterized. It seems like you have less problems like this with outdrives that have the impeller in the drive like the Alpha and Cobra because the water is only pulled up a short distance and then pushed the rest of the way to the engine. With an engine mounted impeller any air leak between the drive water intakes and the impeller will lower water volume and pressure.
I think people have done what you are thinking of but there are also kits to replace the parts that cause the problem, I think Ted did this on one of his, if I recall right. The question I'd have is if you eliminate the water intake on the sterndrive, will it run hotter by not having cooling water coming through it? Maybe that's why some people use both raw water inlets.

 

[kenny nunez]

At this point you have 2 options.
Use heat in the area of the screw and with some vise grips gently try to get the screw to move back and forth while using some penetrating oil which might work.
Shear off the screw and drill and tap new 10/32 threads to remount the sender which I have done in the past.
Trying to drill out the screw that small without some type of jig to keep the drill centered will cause nothing but broken drill bits and an elongated hole.
As Lou said you need water circulating through the drive to keep it cool especially if the exhaust also goes through the housing, Mercruiser and some others make a drive shower kit that will keep the upper half of the drive cool or just leave the hose off between bell housing and transom shield then cap off the nipple in the boat using the forward motion to force water up through the housing.

 

[Lou C]

agreed on using heat for the problem with the screw....might want to heat the area round it and then freeze the screw, the temperature difference might break it free.

Then in the future, any bolts, or screws that go into a transom assembly or outdrive, coat the threads with either Evinrude gasket sealer or Merc Perfect seal and you won't have that problem again. I do this on mine and the bolts don't seize up and this one is in salt water each season for months.

 

[bruceb58]

This is mainly a Merc issue that is exacerbated by having the impeller up on the engine. It can also happen on Volvos and Cobras because there is a plastic water nipple in the pivot housing (bell housing) that can crack if the boat is not properly winterized. It seems like you have less problems like this with outdrives that have the impeller in the drive like the Alpha and Cobra because the water is only pulled up a short distance and then pushed the rest of the way to the engine. With an engine mounted impeller any air leak between the drive water intakes and the impeller will lower water volume and pressure.
I think people have done what you are thinking of but there are also kits to replace the parts that cause the problem, I think Ted did this on one of his, if I recall right. The question I'd have is if you eliminate the water intake on the sterndrive, will it run hotter by not having cooling water coming through it? Maybe that's why some people use both raw water inlets.

The water pump in both the Mercruiser Bravo Drive and the Volvo drives are below the water line. There is NO pumping UP to either of the input of those pumps.

There is a reason Volvo eliminated the impeller on the drive like the Cobra had when Volvo did the joint venture. It's a poor design. Way more likely to get water in your drive from a seal failing. If a seal fails on a Volvo pump, it leaks into the engine compartment and you know its happening. So glad I don't have my poorly designed Cobra anymore.

 

[Lou C]

The water pump in both the Mercruiser Bravo Drive and the Volvo drives are below the water line. There is NO pumping UP to either of the input of those pumps.

There is a reason Volvo eliminated the impeller on the drive like the Cobra had when Volvo did the joint venture. It's a poor design. Way more likely to get water in your drive from a seal failing. If a seal fails on a Volvo pump, it leaks into the engine compartment and you know its happening. So glad I don't have my poorly designed Cobra anymore.

Then explain why I have not had to get it resealed in 15 years? Keep in mind this boat is far from a trailer queen it sits in the brine for 6 months each year.
When a Bravo or Volvo is on plane the raw water intake hose is above the static water line level, any air leaks and yes they can pull in air and disrupt raw water flow.

 

[alldodge]

Fight, fight , fight

Maybe look at it as, if the impeller in the rear of drive was the best way to go, why are they not being used?

 

[bruceb58]

Then explain why I have not had to get it resealed in 15 years? Keep in mind this boat is far from a trailer queen it sits in the brine for 6 months each year.
When a Bravo or Volvo is on plane the raw water intake hose is above the static water line level, any air leaks and yes they can pull in air and disrupt raw water flow.

Because then the speed of the boat forces the water up the inlet hose. Not even an issue once the boat is on plane.

I have two friends that had Cobra leaks at the shaft that drives the water pump impeller. It happens. Volvo decided to abandon that idea for a reason. There were people on here that had the problem as well. The problem is not when it is sitting...the problem is when it is being run.

 

[Lou C]

Because then the speed of the boat forces the water up the inlet hose. Not even an issue once the boat is on plane.
However, if you look in the document that V/P published on overheat diagnosis, you will see that they advise using clear hose between the hose that comes up from the transom to the impeller housing, because, air leaks can develop when the boat's on plane. If it never happened then why would they have this in their own diagnostic manual? Air leaks can also develop around the impeller seals and be drawn in by the pump this is why they advise clear hose on the inlet side and the outlet side of the impeller...

Volvo Penta Overheat Diagnosis - [PDF Document] (documents.pub)

I have two friends that had Cobra leaks at the shaft that drives the water pump impeller. It happens. Volvo decided to abandon that idea for a reason. There were people on here that had the problem as well. The problem is not when it is sitting...the problem is when it is being run.

Yes I had that problem once, in 2004, it was fixed for the 2005 season and never had it again, every year the gear oil looks the same as it did going in.
So yes that can happen, its possible that the seal was improved, but as I said not a repeat problem for me and I've had this one 18 years.


Getting back to the problem, I'd probably repair this using the improved parts that Merc sells to correct the problem, it might not be necessary to go to a thru hull water pick up.

 

[platon20]

OK guys here's the update.

That water hose coupler on the engine side of the boat is a real pain in the ass to get off. I can get the top bolt off, but the bottom one is directly underneath the coupling and you can't see it behind the steering control and all the hoses and lines going back to the transom.

You can't visualize the bottom bolt from lying down on top of the engine. The part of the coupler that sticks out completely blocks it from view. You can barely visualize it when lying down on the side of the engine with your head as far back as it will go to the transom, but it's a good 2 foot distance with only 2-3" of clearance to get your hand back there. All of the online videos show it being removed with the engine being completely hoisted out, which I'm not willing to do.

This is yet another poor Mercruiser engineering design. The picture below shows it well, but that's with the entire engine removed. The clearance between the bolt and the plastic coupler is too small to get a ratchet on. I tried for 30 mins from different angles. Next I tried just a regular crescent wrench, but again the limited clearance between the plastic and bolt makes it impossible to remove from the side. You would have to get completely under the engine and twist it in very small bursts. If only there was about a 1/4" more clearance then the ratchet would have worked.

Since I can't get the interior coupler off, my next best option is to try and patch or use a rubber hose bridge over the gash in the water inlet hose.

If that doesn't work, then I'm going forward with a thru hull water inlet because I'm done twisting my arm into a pretzel trying to reach back there.

 

[alldodge]

Those bolts can be a Beouch to do. With all the stuff on your motor makes it even worst. Probably will come down to what needs to be removed to get at it (exhaust, hoses, other)

 

[Lou C]

Try pinging Ted above I think he fixed this on one of his Bravos...

 

[tpenfield]

As I recall, I had to use a variety of socket and box wrenches to get the hose coupler off. Putting it back on is a whole other trip

While you have the thing off and are replacing the hose, check for Bravoitis and maybe go with the new-style hose kit that helps address Bravoitis.

 

[alldodge]

I did the new style on mine, but I could get to mine from the port side

https://forums.iboats.com/threads/bravo-itis-fix.680176/

 

[platon20]

I did the new style on mine, but I could get to mine from the port side

https://forums.iboats.com/threads/bravo-itis-fix.680176/

Did you have to remove the power steering control/rack or just turn the helm to port?

 

[alldodge]

I just turned the port