38 Top Gun Cooling Problem

[2112]

It is in the extension part of the assembly. You can see it on the fountain because it is with in the transom of the boat . On the ITS it is in the set back. I don't think it is visable unless the engine is out.


I only mention this to make you aware. Your boat is likely too new to suffer from this yet.

Ah, that would explain it. :sifone: I appreciate you making me aware. It will be a whole lot harder to check when everything is back together.

So, did I read you right? you just eliminated the check valve on the air vent? Did you keep the lines small, like a # 6 to keep water bleed off to a minimum?:bigear:
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[2112]

http://www.seriousoffshore.com/forums/showthread.php?t=7931

Wow, That is closed off. I do back flush the inside but I hear you about the outside. Another thing to worry about. :ack2:

Luckily, we are a little less salty out west.
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[MOBILEMERCMAN]

So, did I read you right? you just eliminated the check valve on the air vent? Did you keep the lines small, like a # 6 to keep water bleed off to a minimum?:bigear:
.

They were 120+mph race boats but, yes no valve #8 line. 100mph offers 144lbs of pressure. I think a valve on a pleasure boat is good. Just don't rely on the valve and put the outlet under water off plane.

 

[MERPerformance]

I suggest you always put the dumps below the waterline. It only takes a small piece of grass or debris to hang open a check valve. Once on plane you have pressure in the strainer. Off plane is when you suck in the air.

Also, if you try the clear hose install after the motor before exhaust.

2112 I don't know if you are aware of the potential problem with the intake line restriction in salt water. The place where the intake line comes through the transom. The intake hose tends to get pinched from corrosion. It is easy to inspect if you don't have extension boxes. The cover where you attach the intake line is where you can see the problem if it exists. Two hex head bolts hold the cover on if it is pinched it is immediately obvious when the cover is removed. You should have a new gasket on hand.

I agree, with below the water line is a better installation than what we had on the Top Gun, sorry the thru-transom fittings were already there.
What makes the difference on the clear hose after the engine or between the sea-strainer and the pump if looking for air coming into the system?

 

[MOBILEMERCMAN]

I have two reasons that immediately come to mind. First the pressure before the motor will be greater that the clear hose is designed to handle. Second the water is under pressure collapsing the bubbles. By the time the water has entered the engine the pressure has fallen, the bubbles have expanded and it is easier to see them.

Mercury has recommended 25 lbs at wide open on most engines. In the race boats you only want to scoop what is necessary. I understand 15lbs is the bare minimum an engine will tolerate. If steam pockets are forming adding air to the water it is here where you will find evidence of it.

 

[MERPerformance]

I have two reasons that immediately come to mind. First the pressure before the motor will be greater that the clear hose is designed to handle. Second the water is under pressure collapsing the bubbles. By the time the water has entered the engine the pressure has fallen, the bubbles have expanded and it is easier to see them.

Mercury has recommended 25 lbs at wide open on most engines. In the race boats you only want to scoop what is necessary. I understand 15lbs is the bare minimum an engine will tolerate. If steam pockets are forming adding air to the water it is here where you will find evidence of it.

First of all, I was asking a honest question, with no smartness intended. The clear hose I used is pretty thick, has been on with alot of time in use, yesterday to be a matter fact in the ocean. It's coming off anyways. Also with the issues addressed in this thread, I have read the water pressures at the cross-over, at the block drain and at the intake manifold they haven't been different than 5 psi. What I noticed, before this thermostat housing issue was found that the water pressure would bounce about 5-8 psi at the intake at cylinder # 1 location and that was the steaming affect of the water. I agree with you that 15 psi minimum for this, I also like 25 psi min. pressure we had 25-30 psi, what caused our problem is the cold water from the by-pass confusing the thermostat, allowing the water on cylinders 1-7 to develope steam pockets, and you are right in saying that using the clear hose between the engine and the exhaust would show the bubbles. Our problems came from a part that wasn't engineered the same way that Stainless Marine designed their's. What have you seen for pressure drops from the sea strainer to the water inlets on the block. Thanks Mark

 

[MOBILEMERCMAN]

Mark, I am not an engine guy, I am only sharing what I have learned while rigging and racing boats. I have been fortunate to work with some great people and have witnessed much in the progression of water systems in Fountain race boats.

The last thing I have to add with the clear hose is you can extend it into the cockpit and monitor it easily while underway.

Thank you for the thread, following it though, and sharing your results.

 

[MERPerformance]

Mobilemerman, went back and read your post on the clear hose, at that time I was looking at the water pick-ups, merc water dumps and sea-strainers. I saw you said; between the engine and the headers. Sorry you had to repeat that to me, I over looked that.

 

[MERPerformance]

Thanks Jim, you have great knowledge. I usually don't have to get into rigging issue of this kind, as you can see, something not tested for every application.

 

[MOBILEMERCMAN]

What have you seen for pressure drops from the sea strainer to the water inlets on the block. Thanks Mark

I have only attempted to measure in the stainer unsuccessfully. AT test between 130 and 140 mph the 250 lb gauge would explode in one short test run. I would read the pressure in the block drain. I never experimented with the areas in between. The focus was on carrying just enough pressure to keep steam from forming and passing only water void of air through the engine. The engine guys we worked with dealt with the issues of flow through the engine as you have here. That part I have no experience to assist you with.

 

[MERPerformance]

I guess I can close this subject one this. Heres the deal: Water cross-overs and thermostats housings are not created equal. Eddie Marine needs to change the design for HP, not drill holes in the thermostat until nothing is left of it. Stainless Marine has it engineered correct, keep the by-pass water away from the thermostat confusing it. What did it take to fix: plug the by-pass on the cross-over and drill & tap the front side of the intake to 1/2 npt and by-pass warm water to the thermostat housing with #10 an. Temps stay between 140 -150 degrees at all rpms and after bringing off plane back to idle in gear.

 

[MERPerformance]

I have only attempted to measure in the stainer unsuccessfully. AT test between 130 and 140 mph the 250 lb gauge would explode in one short test run. I would read the pressure in the block drain. I never experimented with the areas in between. The focus was on carrying just enough pressure to keep steam from forming and passing only water void of air through the engine. The engine guys we worked with dealt with the issues of flow through the engine as you have here. That part I have no experience to assist you with.

I never knew the water pressure was that high at those speeds! that will for sure blow some hoses off. I thought maybe somewhere around 100 psi max. Shows what I know. Mark

 

[MOBILEMERCMAN]

Not many boats have speedos anymore. Now its all GPS. According to Livorsi a speedo is a pressure gauge where 70 mph is the break even point 70mph =70 or 71 lbs,,,, 100mph=144lbs. Add a little compressed air from under the boat and a few pressure spikes and gauge went pop.