Getting hot at WOT.

[pursuit2460]

I have a 2000 5.7 EFI w/B3 I/O. Here is what I have done and what is happening. The heads have been re-done, new Mercury exhaust manifolds and raisers, new Mercury impeller, I removed the heat exchanger and acid washed and clean out all the passages and a new Mercury t-stat

Now what is happening. This is my first I/O, but very versed in old school 5.0, 5.7 and LS engines. For refrence, I have a Faria gauge for temp and it starts at 120, 3/4 of the way up is a line, then 175 in the middle, the 3/4 further up another line and finally 220. So, at idle, the gauge will read a bit under 175, between the upper line form 120 and 175. I have hit it with a temp gun and it reads 162+/-. Now, at 35-4000rpms my gauge reads a bit above 175. I have hit with the temp gun while underway and it's around 180-185+/-. Today while coming g back in, I always run it WOT for a bit, 4700rpm. The temp gauge rose up to the line right before 220. Unfortunately, I forget to check actual temp with the gun. Water temp today morning was 87*, salt water.
Is it normal for it to fluctuate like that? To me the heat exchanger looks like it can keep up at lower rpms but when WOT it can't. I also know that these iron blocks run hit and can got to around 220-225. Should this be a concern? Also what are the approximate temp numbers for those 2 line on the gauge.

 

[tank1949]

Bravo-itus????? Salt used??? Check it out! Did this happen before on the older motor? Temp guns are not perfect. I've owner 2. 1 differed from the other one by 10 degrees. Have you checked its accuracy? Have you replaced temp sensor on motor? If so, did you use a lot of Teflon tape or some other sealant that might cause a grounding issue. Years ago, I had a temp switch (not sender) failure because I used excessive tape. Are you testing temp on garden hose the same as in the salt water?

 

[kenny nunez]

You have a case of “BravoItis”. A common malady. Air or exhaust gases are being introduced in the incoming water. Also the water passages on Bravos tend to get pinched off from corrosion over time. Add a section of clear hose to the hose from the drive before the pump. If you see bubbles then there is air getting into the water supply,
You could also have a head gasket problem where combustion gasses are building up enough pressure to overcome the pressure from the raw water pump. Add a section of clear hose to the outgoing cooling water at the thermostat housing. If you see bubbles then it is the head a gasket.
If the engine checks out good then add the thru hull fittings.
These are the parts you need. They are marine grade bronze fittings made by Groco and here are their part numbers.
IBV 1000 valve
STH 1000 W intake strainer
PTH 1000 1”NPT x 1” hose barb nipple. All fittings are 1” NPT 2 of
1” bronze “T” fitting
You will need some other fittings and you want to connect the drive supply water with the thru hull incoming water then to the raw water pump.
That way you will be able to run the boat on the trailer with a flushout.
And have water cooling the oil in the drive.
If you go on the Donzi site this is the cure for high speed overheating.
Since you are handy with the tools I am sure that you can handle this. The biggest challenge will be locating a convenient location for the thru hull fitting, and taking care for trailer board clearance.

 

[Scott Danforth]

Anything over 180 is an overheat

Running hot is lack of water flow. Bravoitis limits water flow.

Remember, your exhaust is a bunch of rubber hoses that melt around 250. As your water flow diminishes, the exhaust temps go from 200ish to 1100idh

 

[pursuit2460]

Bravo-itus????? Salt used??? Check it out! Did this happen before on the older motor? Temp guns are not perfect. I've owner 2. 1 differed from the other one by 10 degrees. Have you checked its accuracy? Have you replaced temp sensor on motor? If so, did you use a lot of Teflon tape or some other sealant that might cause a grounding issue. Years ago, I had a temp switch (not sender) failure because I used excessive tape. Are you testing temp on garden hose the same as in the salt water?

When I first bought the boat I had the heads removed to remove 2 corroded spark plugs. Never ran it before that. After I did the heads, I took it out and it was just above 175. Then one day, it shot up to almost 220. Backed off and it cooled down. After that I did everything mention in my first post and now here I am.
Yes, temp guns are not perfect but have no other way to check. So its temp gun and gauge as of now.
Havent replaced the temp sensor, for all I know it's the OEM one. The boat was a 1 owner and engine was pretty much original.
Temp on hose is solid at around 162-165 on temp gun and slightly below the 175 mark on the gauge.

 

[flashback]

I have a carbed sbc and it cooked the exhaust hoses because the elbows were rusted shut.

 

[pursuit2460]

You have a case of “BravoItis”. A common malady. Air or exhaust gases are being introduced in the incoming water. Also the water passages on Bravos tend to get pinched off from corrosion over time. Add a section of clear hose to the hose from the drive before the pump. If you see bubbles then there is air getting into the water supply,
You could also have a head gasket problem where combustion gasses are building up enough pressure to overcome the pressure from the raw water pump. Add a section of clear hose to the outgoing cooling water at the thermostat housing. If you see bubbles then it is the head a gasket.
If the engine checks out good then add the thru hull fittings.
These are the parts you need. They are marine grade bronze fittings made by Groco and here are their part numbers.
IBV 1000 valve
STH 1000 W intake strainer
PTH 1000 1”NPT x 1” hose barb nipple. All fittings are 1” NPT 2 of
1” bronze “T” fitting
You will need some other fittings and you want to connect the drive supply water with the thru hull incoming water then to the raw water pump.
That way you will be able to run the boat on the trailer with a flushout.
And have water cooling the oil in the drive.
If you go on the Donzi site this is the cure for high speed overheating.
Since you are handy with the tools I am sure that you can handle this. The biggest challenge will be locating a convenient location for the thru hull fitting, and taking care for trailer board clearance.

Thanks for the info. Never heard of "Bravoltis". Have to do some googling on that and get informed on it.

 

[alldodge]

Don't replace temp sensor unless testing indicates it's where the fault is

With heads being removed prior, there now might be an issue with a head gasket leak. If head was not checked for flatness, it could have been put back on and now the gasket leaks

Can verify a gasket leak with compression test

 

[pursuit2460]

Don't replace temp sensor unless testing indicates it's where the fault is

With heads being removed prior, there now might be an issue with a head gasket leak. If head was not checked for flatness, it could have been put back on and now the gasket leaks

Can verify a gasket leak with compression test

The heads were sent off to a machine shop for a full rebuild. I would think that they are flat. I did all the work myself as I have done in the past. Used Fel-Pro Marine head gaskets. I will do a compression test and see where I am at. Other than the overheat, engine runs strong and starts right up. No water in oil either. I just started looking at the Bravoltis issue and ran across your post when you did yours.

 

[pursuit2460]

@alldodge the compression test. Starting at number 1. 190-175-175-180. Now cyl 3&5 where half way between 175/180, I just went with the lesser. Cyl 2-4-6-8 all 190.

 

[alldodge]

While numbers are high (probably a gauge issue) they are within 10% of low to high so should be good

 

[pursuit2460]

While numbers are high (probably a gauge issue) they are within 10% of low to high so should be good

Are you saying those numbers are high for a 2000 TBI 350 w/vortec heads? Right after I wrote this I googled what the comp should be and most where saying 180+. It is a normal comp gauge, nothing fancy, it's an Accutron. Also, since it's with in range I should move on to the water pick up side.

 

[alldodge]

My manuals show 150-160 but all good

 

[pursuit2460]

Well, you guys called it. Bravoltis, it is. Got home today and took off the inner fitting and it is almost all closed up. Guess I will be ordering the kit to fit it.