2006 Mercruiser 350 BIII Hot Manifold?

[WhyKnott]

The replaced 2 gaskets comment leads me to believe they were the wrong ones, otherwise why were they replaced :noidea:

Here is what the gasket should have looked like


This is for closed cooling

I would agree! Does not make much sense - I would assume if pulled apart then they should be able to be reused. His only comment that got me, was that it still ran hot afterwards. Maybe it's the ball valve though?

 

[alldodge]

Post a pic of the engines

Try this, remove the hose from the thermostat housing to the bottom of the manifold, and also the one going to the riser. Put a garden hose on the one going to the bottom of the manifold, and place the other hose in a bucket. Turn water ON going to the manifold and see how much water comes out the riser

 

[rickasbury]

no- if it is scored then for most practical sense it is done. The impeller has to seal top and bottom so if you sand it smooth, your making the chamber taller giving it less seal and making it worse. I only mention it because folks are coming up with a lot of gloom and doom and I also find myself going to the worst case when it is something simple. What I did on mine, there is a company that makes special stainless steel plates that go into the pump housing top and bottom and they make a special impeller that is just a tad shorter so you get that seal back again. I was amazed as to how little scouring it took to be a problem- my pump body is brass, you get into some sand and it really puts a hurting on it fast. I tried to find it real quick- if you need it, maybe I can find the company at home on my computer there.

 

[WhyKnott]

Post a pic of the engines

Try this, remove the hose from the thermostat housing to the bottom of the manifold, and also the one going to the riser. Put a garden hose on the one going to the bottom of the manifold, and place the other hose in a bucket. Turn water ON going to the manifold and see how much water comes out the riser

Excellent, will do! When the boat gets here, I'll go ahead and update this thread with findings. I did ask the Surveyor to forward all the photos of the manifolds - he mentioned the following:

"As for the thermostat housing…..this is what I told the mechanic to look first as ONLY that manifold was not getting the proper water supply."​

So, it looks like in his Infrared pics, he only spotted the starboard engine, port side manifold becoming hot. Everything else was fine, which is why he did not include the other pics in the survey report. I am getting the rest of them to compare temp differences. ​

 

[WhyKnott]

Just a quick update.. it has a 3 point drain system

 

[QBhoy]

Hi.
Just a quick observation.
You mention that on sea trial you made all specified rpm etc. But Earlier it mentions the engine was wot at 4200 rpm.
This is no where near the rpm range of 4600-5000 rpm, which the 350 mpi should be working within. Preferably nearer the top end of that even.
So it appears that the engine is seriously labouring.
Likely there is an underlying overheating issue, but the above worth a serious thought no matter what.

 

[QBhoy]

Hi.
Just a quick observation.
You mention that on sea trial you made all specified rpm etc. But Earlier it mentions the engine was wot at 4200 rpm.
This is no where near the rpm range of 4600-5000 rpm, which the 350 mpi should be working within. Preferably nearer the top end of that even.
So it appears that the engine is seriously labouring.
Likely there is an underlying overheating issue, but the above worth a serious thought no matter what.

 

[WhyKnott]

Hi.
Just a quick observation.
You mention that on sea trial you made all specified rpm etc. But Earlier it mentions the engine was wot at 4200 rpm.
This is no where near the rpm range of 4600-5000 rpm, which the 350 mpi should be working within. Preferably nearer the top end of that even.
So it appears that the engine is seriously labouring.
Likely there is an underlying overheating issue, but the above worth a serious thought no matter what.

So I completely misspoke! I went back over the Survey results and the engine was running between 4800-4900 RPM with a top speed of 42 MPH based on GPS. The engines sounded fantastic, I did not hear any laboring. I did hear some popping but I'm assuming it's from old fuel and lack of an engine tune-up in several years.

 

[WhyKnott]

So I officially have the boat up here, finally! It is dry-docked for now until the Mohawk River comes up a bit and our docks get placed in.

I did want to mention that the engine with the hot manifolds, it did overheat a few times due to the Bravoitis. Would the flappers cause issues with water not exiting the manifolds fast enough? I'm just wondering if they are stuck half open or closed. I'm also looking into that diverter valve mentioned at the thermostat housing within the water path.

 

[alldodge]

it did overheat a few times due to the Bravoitis.

Don't see the flappers causing a restriction unless they broke off and are at the bottom of the Y pipe. If they where down at the bottom then the motor would also have trouble reaching WOT because of the exhaust restriction.

Being a B3, remove the props and see what the exhaust openings look like and if they are clogged up some. Also being a B3 it should have an exhaust tube and not a boot

did hear some popping but I'm assuming it's from old fuel and lack of an engine tune-up in several years.

The popping normally comes from the motor running lean. If (the big IF) it is running lean, this will increase heat to the motor, but can also damage the motor due to detonation

 

[Lou C]

That oil filter looks like it is as hot as the manifold, Make sure you are using a heavier vis oil than the typical car oil. Not a 10/30 or 10/40 but a 20/50 or the Merc 25/40. A lot of people use 15/40 in the Rotella or Delo brands.

 

[WhyKnott]

That oil filter looks like it is as hot as the manifold, Make sure you are using a heavier vis oil than the typical car oil. Not a 10/30 or 10/40 but a 20/50 or the Merc 25/40. A lot of people use 15/40 in the Rotella or Delo brands.

Will do! I'm planning to do an oil change next week on both of the motors and was going to use the Merc 25/40 Synthetic Blend. I'm not sure what type of oil is in there now.

 

[QBhoy]

The popping could be the limiter, given the new info about your RPMs. If your tacho is slightly off (as they usually are) it could be limiting at the usual 5100rpm set point for these engines ?

 

[WhyKnott]

Hi Folks!

Resurrecting this thread as Why Knot has just been dropped in the water in Upstate NY! I finally got around to changing the oil in both motors along with the oil filters. I swapped over to 25W-40 Synthetic Blend, all Merc Parts and Oil. I also swapped out the Fuel Filters and Fuel Filter Basket on the Gen 3 cooling modules.

Interestingly, on the motor I started this thread about with the high Manifold temps (200+), I hear some clicking action from it. Almost sounds like a bad lifter but I know that (or think) that can't be it... been reading up that sometimes the 'clicking' action is taken as a bad lifter but it's the flaps from the motor overheating previously. It has overheated before - Could the flaps being causing the issue with the manifolds becoming hot?

 

[alldodge]

The older motors used metal flappers an rubber rings (not really a ring, but have no better word) around the other edges. So over time or an overheat the rubber would fall off leaving only the metal flap. This can give a ticking sound something like a lifter. If you give it some more rpm's then it goes away