Hotter water and steam coming out of starboard exhaust tip

[snowman51789]

96 mirage 26' with a single EFI 454 mag 385hp with a bravo 1 drive. Dedicated thru hull exhaust (no captains call) and no mufflers

Last night and a few days ago I noticed that my starboard exhaust had what looked like steam (it disipated less then 10' behind the boat) coming out of it. when we got to the beach I noticed that the water coming out of the starboard exhaust was noticeably hotter then the port side. Starboard water was to hot to leave my hand under it, port side water was hot but I could leave my hand under it.


Ive done done researching and I belive I know what causes steam to come out of the exhaust but I was unable to find anything that would be causing this only on one side. Could it still be the water pump? I believe its 3-4 years old.

 

[wahlejim]

How is the volume of water? Water follows the path of least resistance. Right now, I would assume that the least resistance is through the port side, which is cooling it more effectively. There may be some resistance on your starboard side causing the water to stay in the system longer and get hotter.

As long as it is within your safe operating range, I wouldn't worry about it to much. All boats encounter temperature variances between the two sides. It is a never-ending wormhole that you would be digging to try and even it out. See if you can get an actual reading of the temperature and that will tell you what you need to know.

 

[wahlejim]

And don't be too concerned about not being able to keep your hand under the water. Even at 160, you will get burned. Try sticking your hand in a freshly brewed pot of coffee and see how long you can keep it there.

 

[snowman51789]

The water volume seems to be good in my opinion. There is a steady stream of water flowing out (plus the water that comes out in a "spray") I think I know of a way to get the water temp. I will try that the next time I'm out.

Any other opions would be appreciated

 

[alldodge]

IMO it shouldn't be that hot in the water, on the hose OK, but not in the water.

What is the water temp where you boat?
You in fresh or salt?
When was impeller replaced?
How old are the manifolds and risers?

 

[Hugh H]

Head gasket is a possibility

 

[snowman51789]

IMO it shouldn't be that hot in the water, on the hose OK, but not in the water.


What is the water temp where you boat?
You in fresh or salt?
When was impeller replaced?
How old are the manifolds and risers?

I agree. The water flowing out the exhaust tip is to hot to touch even after it's been idling for 2-4 minutes. I'm not an expert but to me it seems off

The water temp is about 75 degrees

I'm in fresh water (lake erie) this motor has never been in salt water

I believe the manifold and risers are the originals. The motor is a 98 gen 6 (I just learned that when I looked up the sieral number)

I don't know when the impeller was last replaced (I think 4 years ago. I bought the boat last year) but I know that this is atleast the 3rd season on it. I'm familiar with alpha impeller but this is my first bravo.

Is the impeller in the out drive or is the pump on the motor the only one (beside the water pump)?

Should it be replaced every 2 years like my old alpha?

 

[alldodge]

The impeller is on the starboard side under the manifold and is belt driven. I change mine every two years but many make it 3 years without issue. Check for missing pieces and it could be a piece is restricting on one side

 

[alldodge]

If you have the VST then the low pressure fuel pump is part of the seawater pump. Make sure to check the lube in the pump housing. If lube is thin then the pump is leaking gas in it. Lube should be an annual maintenance check.

http://www.mercruiserparts.com/bam/subassembly/31810/2336/18

If you have cool fuel with the high pressure pump on the port side under the motor then your seawater pump is here

http://www.mercruiserparts.com/bam/subassembly/31810/2336/19

In any case the impeller, wear plate and seals are the same for the impeller

 

[snowman51789]

I changed the water pump, waiting for the weather to clear up so I can try it out.

Is it normal to also change the pump housing to?

How can you tell when the housing needs to be replaced?

 

[alldodge]

Look for scoring, but the stainless steel backing plate gets wear rings and can be flipped over once al use the other side.

Do you have the composite or brass pump housing?

 

[snowman51789]

Shortly after my last post I got busy with life, so..... After I changed the impeller I took my boat out and did not notice a change in how much steam was coming out of the exhaust. We are thing to Florida in April so yesterday I started taking the exhaust manifold off and tried to clean it out with water to see if it was plugged with sand, in my opinion (non educated opinion) I don't thing I got enough sand out of the manifold to say I found the problem. Any other ideas of what could be causing this?
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I have photos but I can't figure out how to upload them from my phone. I will upload them when I get home.

 

[scoflaw]

Seems to be a very common and normal thing on the big blocks

 

[snowman51789]

Every big block (15-20 that I know of) I've seen at the sand bars we go to that has under 1000hrs doesn't do it. Even when I've seen high hour big blocks do it, it's an even amount coming out of both sides. I think it is slightly more common on small blocks. If it was an even amount on both sides, it wouldn't bother me, it's the fact that it's just one side and that it just started doing it about 5 troops into the year.

 

[snowman51789]

I cant seem to figure out how to upload photos. ive uploaded them to my "idea book" anybody know how I put them in the topic form?

 

[snowman51789]

i did a leak down test one the port side of the engine. im getting 60% leak on 2 cylinders, 30% and another and 50% on the other, all were coming from the intake valve. i have not done a leak down test on the other side yet. can heads be rebuilt or do i need to get new heads?

 

[tcroz]

I've owned 2 Bajas with 454s and both always had warmer water on the starboard side 1st one had 500 hours second had 100. Never had a problem with either motor, although I should note that I could still keep my hand under the water.

 

[Bondo]

can heads be rebuilt or do i need to get new heads?

Ayuh,.... Yer local Machine Shop rebuilds heads everyday,.....

 

[snowman51789]

any idea of a round about cost. I have a lot of experance with dirt bike and snowmobile motors but no experierance with car or boat motors. is there anything else I should be concerned about? i.e. since the heads are bad. should I tear down the whole motor and do a rebuild?

I looked up the casting number on the heads (12562934). it came up as heads for a 502. is this something that I should be concerned about? I would think that I should have 454 heads.

the motor is a 98 454 MAG MPI gen 6

 

[alldodge]

I looked up the casting number on the heads (12562934). it came up as heads for a 502. is this something that I should be concerned about? I would think that I should have 454 heads.

The 454 MPI came with 502 heads (rectangular port) and is part of the reason it has 385HP.