My overheating saga

Pirate Lady

Pirate Lady

Well-Known Member
Jun 2, 2020
7,540
Chesapeake Bay, Middle River
Boat Info
Sundancer 250 ‘91
Engines
7.4 Bravo 1
I cant find the original thread so here goes, 7.4 Bravo1, overheated on 6/5 as soon as it got on plane, this was after running 20 mins at 1200rpm. We replaced thermostat, housing, impeller, flushed the engine for hours. Oh and put new manifold risers this winter. So this weekend we take it out first time. 30 seconds on plane at 3400, she pegs at 220, alarm screaming. There is nothing left in bilge to replace.
It will idle all day in slip and never go above 140 but get on plane and it pegs in no time.
Thinking Bravoitis. Outdrive coming off this week to replace the water pickup hose and something else my mechanic said that i don’t know what it is. This has to work, there is nothing else to do.
My guy said new boats bypass this problem by using a thru hull instead of sucking thru the outdrive and this is a possible solution. Anybody know about this?
 
Bravoitus is certainly a concern especially in salt water. I just installed the new water pickup hose on one of my B3 outdrives. Since I have twins pulling the engine was necessary to install the pickup hose which I had to pull anyhow to replace a timing chain/ oil pan gasket. I boat in fresh water and there was no bravoitus present.

To your concern, a boat neighbor was experiencing an overheat condition very similar to yours and after changing every possible cause resolution was had by changing the engine water pump. The recirc pump that bolts to the block.

I am also aware of a couple boaters that have installed the through hull pick up with great success. Doing so requires the block off plate on transom plate water inlet, strainer inside the hull and an inlet strainer on the outside of the hull.
 
Yes on the strainers, had a/c, familiar with that. If open thru hulls on outside it sucks up jellyfish. We tested the engine circulation pump, its passis water thru nice flow.
 
Mechanic just text, he leans to putting in a thru hull. Thru hulls worry me, especially one that must be open all the time, so he gonna pull the drive, inspect, then go from there.
 
Pirate Lady said:
Mechanic just text, he leans to putting in a thru hull. Thru hulls worry me, especially one that must be open all the time, so he gonna pull the drive, inspect, then go from there.
Click to expand...

It’s fair to be concerned about adding thru hulls.
I will say that on my 340DA, I have 4 thru hulls that stay open continuously except when I exercise them monthly.
 
That episode expanded my horizons somewhat. Prior I thought a yellow light meant “hurry because if it turns red then…”
 
I’m also overheating and just can’t figure it out. 01 8.1 horizons. I now have new manifolds, new water pump, new hoses, new thermostat and new heat exchangers. No problems at idle, bring it up to 1,500-2000 rpm and the manifolds and risers get too hot. Someone mentioned there could be an issue with some cylinders running lean. Could that be an issue and this whole water piece wasn’t really the problem?
 
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superwa said:
I’m also overheating and just can’t figure it out. 01 8.1 horizons. I now have new manifolds, new water pump, new hoses, new thermostat and new heat exchangers. No problems at idle, bring it up to 1,500-2000 rpm and the manifolds and riders get too hot. Someone mentioned there could be an issue with some cylinders running lean. Could that be an issue and this whole water piece wasn’t really the problem?
Click to expand...
Well if your riders get to hot that wouldn't make for an enjoyable boat ride. :)

But what is too hot? Have you hit them with a temp gun?
 
Gotta love autocorrect. The port ones get to around 150 before I shut off the engine. The starboard risers and manifolds never go over around 100. After all the stuff all over the water system, wondering if it could be an injector issue. Running lean could cause the overheat?
 
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I have a thru Hull on mine as well as a pickup thru the leg. As long as you put a seacock valve on it they are fine.

the thru hulls are 1 1/4” to match the inlet to the raw water pump, while the B3 inlet is 3/4”. I have never seen a temp over 158 when the thru Hull is open. Temps are in the 170’s when running off the leg.

merc’s recommendation is dual pickups, they Hull and leg. Has worked great for me
 
superwa said:
I’m also overheating and just can’t figure it out. 01 8.1 horizons. I now have new manifolds, new water pump, new hoses, new thermostat and new heat exchangers. No problems at idle, bring it up to 1,500-2000 rpm and the manifolds and risers get too hot. Someone mentioned there could be an issue with some cylinders running lean. Could that be an issue and this whole water piece wasn’t really the problem?
Click to expand...

superwa said:
Gotta love autocorrect. The port ones get to around 150 before I shut off the engine. The starboard risers and manifolds never go over around 100. After all the stuff all over the water system, wondering if it could be an injector issue. Running lean could cause the overheat?
Click to expand...

What propulsion do you have? It's not listed in your profile. If you have Bravo III outdrives in a 380, I would love to see a pic of the immense bilge space you must have.
 
I just added thru hull water pickups with South Bay strainers and thankfully no more worries about Bravoitis. The thru hulls not only eliminate the shrinking diameter of the hose going thru the transom assembly but also increase the volume of water the seawater pump can pickup. I know of several fellow boaters that have added thru hull water pickups and NONE regret it!
 
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