Manifolds, risers, elbows 12 years old

Well I just dodged the mother of all bullets. You know that feeling in the pit of your stomach when you think your motor is shot? I had that since my last post above.

So I sprayed SeaFoam brand Deep Creep penetrating lubricant (no, not the gas treatment - different product) into my spark plug ports. And waited a few days, pulled the crank pulley off. Pulled the top engine water pump pulley off for better clearance. Put the 3 pulley bolts back in and used a pry bar to turn the engine with those partially extended. Was able to rock it back and forth maybe 1/4 turn. That gave me hope. Sprayed more penetrant in the ports, tried again a few days later. It fought me all the way, I cut the sh** out of my knuckle, deep gash, blood everywhere. (But that's par for the course when I work on engines.) Band-aided that. Sprayed more penetrant. Finally today I got the motor to turn all the way around, fighting me all the way, rotated a second rev, then a third. Finally I chanced trying the starter, and she turned round and round. WooHoo! Put the plugs back in and wires and pulleys and belt back on and it started right up. Dodged a major bullet there. Whew!
Sea trial tomorrow... I may still need a seawater pump, but I just changed the impeller last year so I'm not changing it automatically yet.

In retrospect I realize that I erred when I pulled the risers and manifolds and left the motor exhaust ports open, exposed to the elements, Florida salt air, rain, for over a week. Water got in there even though the cover was on the bilge. Moral of the story: Don't be a dumbass like me.
Thanks all for the advice.
 
If you didn't drain the manifolds before pulling the risers were removed, then it probably got in thru an open valve. Good luck with your engine, but it definitely had some life knocked out of it.
 
Update: So I got my engine running. Still have the initial problem of overheating though. I had changed the manifolds, risers, and elbows. I made sure the orifices were lined up as on the original manifolds and risers. Still over heating. Then I pulled the raw water pump, even though I had just changed that last year. Opened it up and the impeller looked fine, all over. No cracks or tears. Then I changed the thermostat, same rating 160F. Still overheating. I am out of ideas.
Here is what it does:

Leaving the dock is a no wake zone for a good 10 minutes, I run at a bit above idle, about 900-1000 rpm and temp climbs to 170-175. Not happy with that.
Then I get into a bayou and open it up to 3800 rpm. Temp drops back to 160 quickly. Small bayou, less than a minute to the next bridge. I slow down to 1000 rpm again for 5 minutes into next channel no wake zone. Temp is about 170 again. Then I get out to the open Tampa Bay and open it up WOT. 4000 rpm or a bit more. Engine sounds good. I throttle down to 3800. After 1 minute temp climbs to 180 then over that and then engine rpm drops to 3000 on its own. (Yes I get that this is a computer controlled safety feature). Temp keeps climbing, I throttle back to idle, temp keeps climbing 185+, I kill the engine and sit for 2 minutes. I start up and throttle up to 2000 rpm and the temp drops down to 170. I hobble back to my dock keeping barely on plane, and then 900 rpm in the no wake zones.

So after changing the manifolds, risers, elbows, thermostat, and checking the raw water pump, .. whats left? Ideas?
 
When you swapped out the raw water pump, was the impeller in one piece? If not, did you find all the pieces?

Im not savvy with the B3 and your setup - but is your raw water intake from the drive, or from a thru hull? Also assuming raw water cooled? Is the B3 the one thats can end up with Bravoitis?
 
Last edited:
This post is a bit confusing as it appears it was started by another member.
When you chiselled the broken pieces out of the exhaust, did you get it all? Does not appear so from the pics you posted. Did you remove the Y pipe to make sure there isn't a restriction in the bottom? The flappers at the top of the Y pipe will not take a lot of high temps. They too can fail and drop down.
Have you been monitoring the manifold temps? It is a good indicator of raw water circulation. You should be able to hold your hands on them.
4000 rpm is low for WOT. You are low in HP or over propped.
 
When you swapped out the raw water pump, was the impeller in one piece? If not, did you find all the pieces?

Im not savvy with the B3 and your setup - but is your raw water intake from the drive, or from a thru hull? Also assuming raw water cooled? Is the B3 the one thats can end up with Bravoitis?

Impeller was in pieces, and yes I got them. I found the broke pieces in the pump outlet hoses and re-assembled the old impeller to verify that I had them all.

Not sure where the water comes in. Per the mercury parts catalog for my S/N it comes in thru a transom hose. I will go look to verify. So I just googled bravoitis. So that's actually a THING. Wow. Thanks, I have some research and inspecting to do. And that's what I appreciate, just someone giving me a direction of where to look for probable issues. Thanks.
 
This post is a bit confusing as it appears it was started by another member.
When you chiselled the broken pieces out of the exhaust, did you get it all? Does not appear so from the pics you posted. Did you remove the Y pipe to make sure there isn't a restriction in the bottom? The flappers at the top of the Y pipe will not take a lot of high temps. They too can fail and drop down.
Have you been monitoring the manifold temps? It is a good indicator of raw water circulation. You should be able to hold your hands on them.
4000 rpm is low for WOT. You are low in HP or over propped.

Yes, I may have hijacked the post which was about rusted risers. My posts here progressed from changing the manifolds, risers, and elbows, to "why is it still overheating?" To your question, yes I chiseled the pieces out of the rubberized exhaust connector that the elbow attaches to. And no I didn't investigate further down so Thanks for mentioning that, I have some inspection to do. The manifolds didn't seem to be unbearably hot.
I think Im doing a bit better than 4000 rpm, maybe 4200. What's normal for a 2003 5.0 MPI ? Compression checks were within limits last time I did them, all between 170 - 180 psi.
 
Does your engine have the original cover over the flame arrestor? It should list it's specs along with the s/n's of the original engine, transom assembly and outdrive. If all numbers match up, you will have an idea where you should be assuming props haven't been changed. Your engine should be somewhere between 44-4800 @ wot.
From what you have posted, a raw water circulation problem is indicated. Did you check your manifold while the engine temps were high? Excessive exhaust backpressure can effect both temp and performance and is why it was mentioned.
 
Did you have water or fuel seep into your oil? I have a similar problem. Have 2008 260HP Mercruiser with Bravo III was out 20miles stopped the engines. Restarted my port engine but starboard was struggling to turn over. Boat was running fine to this point. No overheating or funny sounds. Thought I had hydrolock. Replaced starter....was able to get engine to turn over but not start. Removed plugs and water was in all 4 pistons on the right side. Also oil level looked good but high. Removed manifold/risers and noticed rust in manifolds, but when I started to drain the oil I pumped out over 1/2 a gallon of water...…
question 1. The engine still turns over but is the engine shot? Considering the oil is with water?
Question 2: Is it worth it to replace the manifolds/risers/plugs /oil and see if engine is still good and compression is good?
Or am I wasting my time and energy.
Any help would be great.
 
Not sure what you mean by double hijack? Meaning I'm basically screwed....lol?
 
20190831_143825.jpg
This post is a bit confusing as it appears it was started by another member.
When you chiselled the broken pieces out of the exhaust, did you get it all? Does not appear so from the pics you posted. Did you remove the Y pipe to make sure there isn't a restriction in the bottom? The flappers at the top of the Y pipe will not take a lot of high temps. They too can fail and drop down.
Have you been monitoring the manifold temps? It is a good indicator of raw water circulation. You should be able to hold your hands on them.
4000 rpm is low for WOT. You are low in HP or over propped.
Finally took the elbow off again, and the flex exhaust tubing. I see a hard oval tube in the bottom behind the motor. It has some kind of rod going through the middle and some deformed rubber thing straddling the rod. Must be the flappers. I can't tell but can this (Y-pipe?) be removed from the bilge or do I need to have the outdrive taken off the back to get to it?
 
Last edited:
Why would you want to take the y-pipe off ? No need unless it's leaking at the mounting surface, them flappers just pull up and out
My exhaust elbow was completely rusted. (scroll to top of this thread for picture) I replaced manifolds, risers, elbows, thermostat, removed raw pump and visually inspected impeller. Engine overheats at cruising rpms. Found one chunk of rusted metal wedged in upper exhaust tube. Maybe something is wedged way down there where I cant see it.
 

Forum statistics

Threads
112,946
Messages
1,422,763
Members
60,929
Latest member
Henchman
Back
Top