38 Top Gun Cooling Problem

[MERPerformance]

How did you modify the sportmaster pick ups and do you have a picture of the air dump/check valve attachment point on your strainers?

What raw water pressure are you looking to get?


Much appreciated

Remove lower set-up in milling machine, use an end-mill and cut lead-in groves and blend.
You have to buy, top caps from Byng, that are for dumps, they are coned and are theaded in the center. You can buy, brass 3/4 check valves at a plumbing supply store,install them with over board dumps to the rear of the hull, I used #8an fittings.

[MERPerformance]

I called Eddie Marine , after doing this to advise them of this issue, they said; wish I would have called sooner, I told them, I wanted to know what was causing this problem. They say, drill more holes in the thermostat, that might be fine for 500 hp, so we talked about blocking the cross-over and taking the water from the front of the intake manifold, the flat area on the front, I already had it drilled and tapped for 1/2 npt, ran a short jumper from there to the top of the thermostat housing which keeps the water temp from confusing the thermostat. It worked great, no more than 150 degrees, cylinder heads even in temp all four corners. They said;they wouldn't modify it because they don't sell many of them. My advice; buy them from Stainless Marine, they will cost more but, worth it in the end.
Water pressure is 30 psi, have to raise pick-ups some more, I like to have about 25 psi@ wot

[2112]

Remove lower set-up in milling machine, use an end-mill and cut lead-in groves and blend.
You have to buy, top caps from Byng, that are for dumps, they are coned and are theaded in the center. You can buy, brass 3/4 check valves at a plumbing supply store,install them with over board dumps to the rear of the hull, I used #8an fittings.

Byng? Is that someone at MM? Could you just drill and tap your current lids or is the cone top critical?

Thanks



.

[MERPerformance]

Byng? Is that someone at MM? Could you just drill and tap your current lids or is the cone top critical?

Thanks



.

Doc. Byng, is M.M., the top is critical to keep the air centered. I know Stainless Marine has a dump valve also for air. I would be afraid to drill a clear top like Hardin, plus the hold-down is in the center.

[2112]

Doc. Byng, is M.M., the top is critical to keep the air centered. I know Stainless Marine has a dump valve also for air. I would be afraid to drill a clear top like Hardin, plus the hold-down is in the center.

I will call him Monday morning. I already have MM strainers, hopefully the cone top just spins right on what I already have. Did you get the Dump valve from Stainless Marine or did you just use brass check valve?

Thank you!

[MERPerformance]

I will call him Monday morning. I already have MM strainers, hopefully the cone top just spins right on what I already have. Did you get the Dump valve from Stainless Marine or did you just use brass check valve?

Thank you!

Yes, you'll get new tops that spin on, powdercoat to match. Tell Byng,I sent you Mark from S.C. we go back to 1995. You can get the check valves from the hardware store, try to get something like 1/2 npt, I could only get 3/4, its a backflow preventor, the tops are going to be 3/4 npt, use a 3/4 -8an 90 degrees, then use -8 push lock hose run it to the transom with thru hulls and adapt the check valves there, that way you won't see the brass or you can try to locate some stainless ones. I take it you have a step- bottom, are you getting air in the system, have you checked it with a clear plastic hose first?

[2112]

Yes, you'll get new tops that spin on, powdercoat to match. Tell Byng,I sent you Mark from S.C. we go back to 1995. You can get the check valves from the hardware store, try to get something like 1/2 npt, I could only get 3/4, its a backflow preventor, the tops are going to be 3/4 npt, use a 3/4 -8an 90 degrees, then use -8 push lock hose run it to the transom with thru hulls and adapt the check valves there, that way you won't see the brass or you can try to locate some stainless ones. I take it you have a step- bottom, are you getting air in the system, have you checked it with a clear plastic hose first?

Thanks,

Yes stepped bottom, Pressure stays constant @ 15lbs but that doesn't mean it is all water. No, I have not done the clear hose test, but I recall seeing it mentioned somewhere, maybe this thread. I will go back and check.

Of course at idle and cruise, everything is fine, it is on hard runs that my temps spike and when I slow to cruize, they come right back down pretty quick. I highly suspect air in the raw water.

On a related note, when I took Tres' course a few years back, he told me to put drive spacers on my Gladiator for "many reasons". I thought at the time he meant handling, maybe better water intake was also a factor?
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[2112]

I forgot, Is there a specific pressure setting on the check valve or just make sure it a one way proposition.

Thanks for your advice. Will call Byng Monday morning.

[MERPerformance]

I forgot, Is there a specific pressure setting on the check valve or just make sure it a one way proposition.

Thanks for your advice. Will call Byng Monday morning.

I think maybe 5psi. It's really only there so you are not sucking air back through the dump lines.

[MERPerformance]

Thanks,

Yes stepped bottom, Pressure stays constant @ 15lbs but that doesn't mean it is all water. No, I have not done the clear hose test, but I recall seeing it mentioned somewhere, maybe this thread. I will go back and check.

Of course at idle and cruise, everything is fine, it is on hard runs that my temps spike and when I slow to cruize, they come right back down pretty quick. I highly suspect air in the raw water.

On a related note, when I took Tres' course a few years back, he told me to put drive spacers on my Gladiator for "many reasons". I thought at the time he meant handling, maybe better water intake was also a factor?
.

If you are running thermostats, that seems to be the readings you would get. As we have talked about, many do not like thermostats, running with out them hides alot of problems. I'am almost sure you are getting air in the system. With a sportmaster drive even with the water inlets, they will need to be opened up to allow more volume of water. I know from Bob, that you can handle a small grinder. I'll try to get some pics for you. As far as the drive spacers go, I don't know! not a correction for water issues for me. Have you done back to back testing on speed and slip factors. If you have a standard lenght lower and it's a sportmaster, it was designed for hi speed, but: it has more area which is causing drag. Example: the 2004 Top Gun I just did some 604 for has standard lenght sportmasters, before this boat ran 92-94 mph @ 5450-5600 rpms, we are still playing with props, have tried a P5x 32 92mph @ 5050 rpm, 34 bravo one 91mph @ 5000rpm, going to try 32 bravo ones lab from there. Probably get 95-96 mph@ 5500rpms. These engines were 735hp@ 5600 rpms now we are at 815 @ 5900, we are only going to give him 5600rpms max, the owner only knows two positions idle& W.O.T. We were expecting higher speeds,but without a 2"shorter lower not going to happen, two other boats out there one with 850 hpmax speed 101mph, the other 750hp 2"shorter same speed. If we raised the rpms, we could get closer, but with out the - 2" falling way short.

[2112]

Yup, I have Sportmaster shorties. And they are mounted high. I have not calculated slip because I am already knocking on the door of desired speed with 30" P5s (labbed) at 6,000-6200rpm or 32" 4 blade B1s at 5700-5900 .

My issue is having to get out of it due to climbing oil temps. My closed cooling never exceeds 180 but I have to slow when my oil hits 260-270. As I said, dropping to cruise cools it down fast (220-230). (I have the big Teague oil coolers). PSI stays at 15 but I am relatively convinced I am not getting enough raw water when @ WOT. I also measure temps in the pans BTW.

You have given me a lot to work with here. Thanks.
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[MERPerformance]

Yup, I have Sportmaster shorties. And they are mounted high. I have not calculated slip because I am already knocking on the door of desired speed with 30" P5s (labbed) at 6,000-6200rpm or 32" 4 blade B1s at 5700-5900 .

My issue is having to get out of it due to climbing oil temps. My closed cooling never exceeds 180 but I have to slow when my oil hits 260-270. As I said, dropping to cruise cools it down fast (220-230). (I have the big Teague oil coolers). PSI stays at 15 but I am relatively convinced I am not getting enough raw water when @ WOT. I also measure temps in the pans BTW.

You have given me a lot to work with here. Thanks.
.

Dump the air first, than go for the pick-ups on the drives.

[MOBILEMERCMAN]

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.

[2112]

I don't have extension boxes but I do have ITS. They have rigid (aluminum?) intake pipes coming in through the transom. Is the pinch in between this and the Drive helmet?

Also, are you saying have the air dumps coming out the bottom or just below the water line on the transom? Probably smart to put a screen over the air vent hole in the strainer.

On a side note, I run 1&1/4 raw water lines through everthing untill the y-pipe that feeds my headers, then it is size 12 all the way out to the dumps. Each pipe has a 3/16" hole to mist the exhaust as well.

Thanks

[MOBILEMERCMAN]

The part I am referring to is where the water hose from the drive bellhousing goes through the transom. It is the forward end of number 15

http://www.mercruiserparts.com/Show_...Gimbal+Housing

I believe it would be a pita to check on an ITS. My only suggestion is to back flush through the transom and see if it will take a full stream of a garden hose. The actual passage is only about the size of a finger at that moment and if it is corroded it obviously gets smaller. I think there was another thread on the subject that included pix.

[2112]

And that part feeds into part # 20 in that picture? For ITS, # 20 doesn't exist, it is a long tube that makes a sweep inside the boat.

Either way, I assume there is a corrosion build up at that junction?
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[MOBILEMERCMAN]

Also, are you saying have the air dumps coming out the bottom or just below the water line on the transom? Probably smart to put a screen over the air vent hole in the strainer.

Ideally below the waterline at idle and on hullside where you can monitor while underway. Most have screens of some sort. But as you may know silly things happen. If the dump line is exposed to air the slightest debris will allow air in and create a problem. In the race boats ten years ago we tried many different types of pop off valves eventually we just dumped the air with no valve.

[MOBILEMERCMAN]

And that part feeds into part # 20 in that picture? For ITS, # 20 doesn't exist, it is a long tube that makes a sweep inside the boat.

Either way, I assume there is a corrosion build up at that junction?
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That is an ITS break down I shared. The hose 15 connects the bellhousing where the drive mounts to the transom plate. the insert 16 expands the hose and holds it in place. 20 shows where the larger hose attaches and it runs forward where you can see it and it eventually attaches to the seapump.

When the corrosion builds up it pinches the hose ,collapses the insert, and restricts the inlet of water.

It should take a full stream of a garden hose. If it won't it may be worth checking . I will look for the other thread I mentioned after I eat. My dinner is on the table. I be back soon.

[2112]

That is an ITS break down I shared.

It Looks just like what I have on my Fountain but Cigarette must have eliminated it because # 20 is not anywhere to be seen on my Gladiator.

I back flush this with salt away after every outing and the flow appears strong, I am apart at the moment so I have access to everything. I will check it.

I would be interested in that other thread if you find it. Thanks BTW.
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[MOBILEMERCMAN]

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.

Here is a pic of the a corroded one. It has been my experience it is not a problem before say 5 seasons. Every place is different I have no experience with west coast saltwater. The salt collects between the hose and the housing and flushing has no effect because it is external to the hose spraying soap and salt away into the hidden areas of the gimble ring area may help.

http://www.seriousoffshore.com/forum...ead.php?t=7931

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