Logo
FULL SITE MENU

1994 mercruiser 7.4ltr bravo one.

W

Worknssv

New member
Good evening/morning,

My name is James

Im new to the forum, and would like to ask your advise please.

I am sure this has been covered somewhere, I just couldn't find it.

I recently purchased a 1994 searay select. It have a 7.4 bravo
in it.

it had been in storage for 7 years, boat is immaculate, when I picked it up I sent it streight to the marine mechanic, had the pull the leg and do a service, bellows, shift cables, seals ect.

I then picked it up and put the following on,
new impellor
new water pump
new thermostat
new fuel filter
oil
oil filter
pulled Risers and checked they were new.

After all all this I started it.

engine ran well, running on all cylinders not missing or carrying on. However 10 min in it started getting warm, we **** it off and went on to flushing block and all hoses. Engine never went over 180-190

put it all back together and started it up, it ran bad missing and carrying on. And over heating.

pilled riser off and there was water in exhausts, piles plugs and filled with wd40. Put new manifolds on new riser gaskets and put rusers back. Found bits of impellor in power steering cooler.

started boat and it ran beautiful, didn't over heat and ran perfectly smooth.

desided I would take it to the ramp and go for a run, after a 15min commute to the ramp I backed boat in and started. It
ran horrible again, missing and carrying on.

took plugs out and I had water again!

could anyone suggest what to do next? Could it be inlet manifold? I'm lost.

sorry for long post just wanted to give as much info as possible.

thanks again,

James
 
Why would you put the old exhaust ELBOWS back on? Chances are they are no good also. If the elbows have base bolts, they are probably stainless and should be replaced with the Iron ones.

Did you check you water pump impeller after you found the pieces in the OIL cooler?

How steep was the boat ramp that you used? With some ramps that are steep you back your boat down, until the drive is under water and fire up the engine, then finish backing it down or you will fill your exhaust with water.
 
Docksidemarineservices said:
Why would you put the old exhaust ELBOWS back on? Chances are they are no good also. If the elbows have base bolts, they are probably stainless and should be replaced with the Iron ones.

Did you check you water pump impeller after you found the pieces in the OIL cooler?

How steep was the boat ramp that you used? With some ramps that are steep you back your boat down, until the drive is under water and fire up the engine, then finish backing it down or you will fill your exhaust with water.
Click to expand...

Reason I put old elbows back on is because after my mechanic inspected them he told me they were fine. After I found rubber in the cooler I did remove the pump and pull back plate off. No rubber found. Ramp was a little steep, and yes I did back it in and then start it, never has this problem before.
 
Worknssv said:
Reason I put old elbows back on is because after my mechanic inspected them he told me they were fine. After I found rubber in the cooler I did remove the pump and pull back plate off. No rubber found. Ramp was a little steep, and yes I did back it in and then start it, never has this problem before.
Click to expand...

Did he test them or just look at them?
 
After sitting for so long, What I would look at next is the thermostat.

It may be stuck/seized.

For a quick test remove it and see if temps stay low and the water flow is good volume.

I would replace it simply as a preventative measure.

If this is a raw water cooled (no closed cooling with a heat exchanger) I would use a 140* thermostat.


If that does not do anything to correct the over temp issue then the next place to look at is the outer transom area where the water hose from drive connects to transom.

Chris and myself have mentioned this many times. The junction of that water hose at the outer transom with the one on the inner transom that goes to the water pump impeller housing.

At this junction of the inner and outer transom assemblies the "pinch" method used to hold the hoses is weak at best...... that area get all kinds of corrosion build up and causes the hoses to collapse which then causes a restriction in water flow by as much as 90%...


Only way to tell is to remove the drive, and remove the hoses outside and inside and take a look and make sure the flow is not restricted.
 
Last edited:
kghost said:
After sitting for so long, What I would look at next is the thermostat.

It may be stuck/seized.

For a quick test remove it and see if temps stay low and the water flow is good volume.

I would replace it simply as a preventative measure.

If this is a raw water cooled (no closed cooling with a heat exchanger) I would use a 140* thermostat.


If that does not do anything to correct the over temp issue then the next place to look at is the outer transom area where the water hose from drive connects to transom.

Chris and myself have mentioned this many times. The junction of that water hose at the outer transom with the one on the inner transom that goes to the water pump impeller housing.

At this junction of the inner and outer transom assemblies the "pinch" method used to hold the hoses is weak at best...... that area get all kinds of corrosion build up and causes the hoses to collapse which then causes a restriction in water flow by as much as 90%...


Only way to tell is to remove the drive, and remove the hoses outside and inside and take a look and make sure the flow is not restricted.
Click to expand...


Update.
Have now sorted overheating issue, was this hose between the leg and transom. Thank you all for you knowledge and advice. My only other issue is water making its way to the cylinder. I am going to do a compression test tonight as I think I may have a blown head gasket or intake manifold.

what do you all think it could be? Raw water cooled, exhaust manifoolds are brand new risers are new, thermostat is new water pump is new.

only after the engin is ran and left sit for 30 min and the restarted does it start to miss and carry on, pull plugs and there is a tiny bit of moisture. Clean it all out spray wd40
put plugs in and it runs fine until I turn it off and then have to repeat the process!
 
Doubtful on the head gasket and definitely not the intake manifold.

Chances are you have a bad/defective(it happens, especially with cheap after market parts ) exhaust manifold, leak between the elbow and the manifold or a bad elbow.

I know you said your mechanic pressure tested the elbow( still wondering on that one)

I still am leaning to the elbow.

Pull the elbow and dry it out. turn up the flange side and pour rubbing alcohol into the water passages. If it is bad you will see the alcohol seep through to the exhaust side.




only after the engin is ran and left sit for 30 min and the restarted does it start to miss and carry on, pull plugs and there is a tiny bit of moisture. Clean it all out spray wd40
put plugs in and it runs fine until I turn it off and then have to repeat the process!


To prove the exhaust is the issue, run the engine until hot and while it is running pull the hoses off the bottom of the exhaust manifolds draining out all the water, then shut the engine down, Do this quickly, maybe have someone help you.

If it restarts with no issues in 30 minutes you are leaking water through an exhaust part or elbow gasket.
 
Last edited:
Back
Top