my 2003 5.0 mpi bravo3 overheated last weekend - video

[HavreDeGrace2400]

Hi, so last weekend i overheated. has been running perfect then when i came off plane last time it overheated.

Changed the overdue thermostat and it is a lot better. But still now after a 20 minute drive the temp heats up a little over the normal 175 the gauge always sits on. Then when I come off plane it spikes up and can still trigger a temp beep. Goes down shortly thereafter.

Im expecting to last till november here in the upper chesapeake. Cant just give up now.

My 5.0 mpi bravo3 setup has a lot of hoses. Ive traced the output from my raw water pump - it has two little hoses sticing out that both go to the cool fuel module... then the rest of that tube goes to the power steering cooler.... then the output from that goes down to the bottom of my single drain stup on the bottom where it then goes into a bunch of branches leading to various drains.. and also one tube to the block circulating pump.

I pulled the tube leading off the power steering cooler at the main drain thing... and made a video of the amount of water pushing out that tube.

Does this water output loot diminished from what it shoudl be? This is at 500rom idle... and it seems like cerainly not a bad amount of water.
https://mcatlas.org/filetransfer/Mis...p/IMG_0321.MOV

seems like my water pump is pumping from what im seeing. But i dont know what it shoudl look like at idle.

If the water output is right... how am i stil overheating. Im going to install another thermostat... only $35 so ill give that a shot in the dark.

I have boat PTSD ugh!

[mmwjr]

My first thought is Bravoities which is a restriction in the transom assembly water tube. The water volume in the video looks low to me which supports a restriction. When was the transom assembly last serviced and do you keep the boat in the water?

[HavreDeGrace2400]

Thanks Mike, I wasn't sure how to judge that flow.

Ive had the boat for three years in the silty fresh waters of Havre de Grace, and it winters out of the water. I'm the third owner. The second owner had it in Deale MD for some handful of years. I don't see anything about the transom assembly in his maintenance records.

If it was a constricted water tube (bravoitis) I can't do anything about that until it comes out of the water.

I also am nervous about trying to check and replace the impeller while in the water.

I wanted to make sure I don't have blockages in my hoses and and the PS cooler. Then hold out hope i just have a damaged impeller. I replaced the impeller two springs ago, about 270 hours ago. I wouldnt think it went bad.

But I would think if it was bravoitis that I would have seen some inkling of a symptom prior. It has never had any symptom at all during my three years in fresh water. Though i did make a trip to St Michaels for a few days recently.

When I replaced the thermostat, it looked pretty old and rusty. And replacing it improved the situation a lot. Just a data point about the level of maintenance on the cooling system. I will try replacing that again as a shot in the dark possibility of salvaging the rest of this season.

I will be pulling the outdrive this winter. Will I be able to determine if that is the cause when the drive is off? If it is the cause, I am thinking to install a through hull pickup instead to feed the raw water, as I have heard is a common thing people do. What do you think about that?

[mmwjr]

Try testing per this link. You should be able to fill a 5 gallon bucket in 15 seconds. This is from the raw water supply hose to th3 thermostat housing.

https://www.google.com/search?q=flow...client=gws-wiz

[shrew]

Originally Posted by HavreDeGrace2400

If the water output is right... how am i stil overheating. Im going to install another thermostat... only $35 so ill give that a shot in the dark.

Unless you installed a 175F thermostat it is not likely to be the thermostat. The culprits are:

- Constriction where the intake water passes through the transom assembly (Bravo-itis).

- Exhaust manifolds and risers need replacing.

The behavior your experiencing is the engine is coming off plane, as you slow so does the impellor speed and water flow. However, the engine is at it's hottest at that point. Water flow should be sufficient to keep the engine cool.

[HavreDeGrace2400]

I chickened out last week on pulling the intake hose off the water pump. But today i did it and it was no problem.

I've come to grips with the likelihood that i have the bravo-itis flow restriction. I'm ready to pull the drive and remove the bell housing this winter in order to replace the hoses and stuff.

But today i decided to get over it and pull that tube. I managed to get it upright above the waterline more easily than i feared. blew through it to test restriction... it blew easily so hmm. But when i laid the hose down and observed the flow it was really quite meh.

So i removed my toilet hose from it's seacock. The flow on that smaller tube was triple what was coming out of my transom hose. I will be installing a y valve and some tubing tomorrow to connect to my rwa water pump to see if my overheating improves.

If that doesnt improve cooling issue I'll suffer another impeller check/replacement.

Will report back...

[mmwjr]

Based on the flow rate comparison of the two hoses you have confirmed the restriction. Are you sure that you want to gamble the engine by playing further?

[HavreDeGrace2400]

My intake bypass made no difference.

I opened the water pump hoping to see a bad impeller, but it was flawless. Then I noticed the back wear plate was totally fried.



This has gotta be my overheat issue. Can i get a wear plate to put on top.. or some new reasonably expensive housing....

[mmwjr]

You can buy a pump kit that comes with a new housing, wear plate and impeller. I’ll be surprised if this completely fixes the issue.

[HavreDeGrace2400]

Did a lot of stuff changing water pump wear plates, circulator pump, clearing block drains, flushing hoses.

On each side I have a hose in the riser and a thermostat output hose into the bottom of the manifold.

During my hose flushing madness, I found out that the starboard manifold hose is clogged in that manifold. The other three are gtg.

West Marine has a Sierra for 265 I'll be trying tomorrow then another test ride.

I think my lesson learned, is that I should have had one of those point and shoot thermometers where i could have identified a specific location much earlier.

[HavreDeGrace2400]

Installed a new starboard exhaust manifold yesterday and the overheat issue is gone.

I did a lot of other stuff that surely incrementally improved cooling. But surely, it was the manifold that was the main issue.

I didn't really understand the hoses into the manifolds. There's the top hose at the elbows fed directly from the water distribution housing to a T then to each elbow, which is a constant input to the exhaust. Then there are two hoses from the thermostat housing that go into the bottom of the manifolds. I pulled both tubes on each manifold/elbow, then blew into each while holding the other opening closed with my hand. I was able to blow bubbles out the outdrive exhaust from either top or bottom on port. I could blow bubbles out of the elbow hole on starboard. But I couldn't get any air through the starboard manifold hose barb.

I cleaned out the starboard elbow and reused it. Hardest part of the manifold replacement job was rubbing the paint off the gasket surfaces with acetone as recommended by the manufacturer. Took longer than the rest of the job.


I took apart the replaced circulation pump. The impeller was rusty and crusty but looked functional. Dunno if I gained anything there aside from clean and shiny!

I did get a lot of crud flushed out the port manifold drain, felt good about that. And I really worked the two block drains which were largely blocked. This boat has the drain system where the block drains are always plumbed via small hoses to the main water housing on the bottom. Hard to get those hoses off to poke and flush and repeat.

Planning to pull the outdrive this offseason, until now I was planning to pull the bell housing too. Now I'm not sure about that part.

[mmwjr]

Did you go out in this rain and winds to test it?

[HavreDeGrace2400]

I finished it on Friday in time for a sunset test ride. Was a good one !

[mmwjr]

Originally Posted by HavreDeGrace2400

I finished it on Friday in time for a sunset test ride. Was a good one !

Good deal.