Drilling a Hole in Intake manifod
 

Need help please.

i just received my carb engine and it's set up for a serpentine pully system.

my question is... has anyone had to drill a hole in the bottom of the termostat housing placement for an inlet for the hose coming up from the circulating pump. on my 7.4l MPI it had an inlet in the intake manifold for this hose but with the Dart manifold which is on the new motor it does not have one. do i have any other options, or drilling is the only way.

i was tiold the the inlet has to be under the termostat housing . i will post pics if needed or u can look at the velocity thread under prop selection.

thanks

Is this for the by pass hose? And it is also only an issue if you are using the thermostat. No thermostat, no need it.

Jeff,

yes it's for the bypass hose, and i was putting a thermostat in it.

do i have to go this route?
thanks

I don't use thermostats. Unless there is a specific reason that you want to put one in, I would leave it out.

That fitting is so that the exhasut does not run dry when the thermostat is closed. You can plug the pump, and this will increase youre water flow through the engine.

jeff

here r some pics. so if i block the top of the circulating pump, what type of thermostat housing can i use.
i was going to use the standard mercrusier one. would it still work. and i would i get a reading...

do u have any pics i can look at.


thanks

If you have the later model Merc t-stat that looks like picture below, then you do not need to run the recirculating pump to intake manifold bypass. The t-stat housing does not block the flow coming out of the engine like the old style t-stat housings. It merely uses the t-stat to change water direction. Again, it does not block it.

http://images.westmarine.com/large/6937114_hiRes.jpg

This is the T-housing i was going to use. so i'm just trying to figure a way to plumb the water system, where by i don't have to drill to put the bypass underneath the t housing & thermostat.

if u guys have any pics i could see that would be great..

thanks

Drill the manifold and use the bypass

Ditto...
It is also "not" required with the aftermarket unit.
Here shown with the later model Merc unit and aftermarket unit.
Plug it...

I started typing a long response to my studying of this system and just realized I posted this info elsewhere a while ago. Sorry for the link but I said more then (quite detailed) than I could probably do now. Has pics to show water direction also.

Hope this helps.

Post #62 at:
http://marineperformancetechtalk.com...sg5077#msg5077

Nordic,

I guess be careful what u ask for, because it looks like i have to add billet pullies now.lol but those engines look sweet.
please don't mind all the questions cause i'm sort of new to this. so if i plug the cir pump how would water get to the exhaust and would i still use a thermostat.

thanks

Yes, you still use a thermostat. The water exits the thermostat housing to the exhaust.
Once the link that SB is available you will see the flow diagram. These housings always bypass water to the exhaust even when using a thermo. When using a crossover setup and a thermostat you would need a bypass. Two completely different setups though.

Our setups above use a pretty high dollar recirculating pump (Meziere) but are no different in operation than the standard Merc stuff. The setups above with a 140* thermo come up to temp at 140* and never move regardless of how hard we run. 120* thermostats are available if you felt the need.

This is our water system of choice where we deal with large boating water temp swing (37*-80*)

Dave

SB,
that link is not working for me..
but u guys r saying is that i can plug the cir plug. and set the system up as if i had the bypass which i won't and everything will be ok..

I would take the circulating pump off and run a crossover !!!

Merc put a lot of engineering into those thermostat housings. Hold one in your hand and try to follow the passages :D .
This housing bypasses water to the exhaust regardless of the thermostat open/closed state. They also hold the thermostat above the temp senders and above the passage routing back to the circulation pump inlet. This creates a volume of water that is continuously circulated through the motor when the thermostat is closed. It will not allow cold water to enter this circulation path until the thermostat opens.

The small bypass hose traditionally connects below the thermostat on the intake and then to the negative pressure side of the circ pump. Because the Merc housing holds the thermostat above the passage to the 1.75” circulation pump inlet this bypass would just be redundant.

use the SS housing qaberdeen posted and should work fine .....

Ditto! That is the housing I am running on the red motor. Rock solid engine water temps reqardless of lake water temp. What more could you ask. :drink:

(not running a bypass hose by choice, my ciculation pump and intake are drilled for them in case these parts were headed for a car)

Well stated Rage!!
That's why Merc uses them up to their 800s. They have a ton more engineering money than us boys :drink:

Dave

Sorry about that - was down for maintenance but it is back up. My bad.

Here's the link again:
http://marineperformancetechtalk.com...sg5077#msg5077

Make sure you install the spacer, thermostat and internal gasket exactly like the diagram from Merc.
(you can find that on Mercruiserparts.com)
This is critical.

Thanks for all the responses..

The thing is that i Live in Bermuda and it's hard to find quality mechanics because most people down here run out boards and it's only a few stern drive performance boats.. which r efi's or running the cross over system.
i was running a 7.4l MPI and the engine builder built this motor like the 7.4l so i guess i could swap over things. the only thing is i have to finish the plumbing..and i don't want to drill anything..

but it sounds like i don't have to..thanks for the advive. bear with me if i don't comprehen everything, but in a nut shell.. i can plumb the engine as is. i just block off the top of the cir pump and run the hoses the same way..coming up from oil cooler to front right T- housing- out thru d other side to the bottom left side of the cir pump, which puts water into motor. the other two smaller opening r for the hoses from the exhaust manifolds. what temp would i use for the thermonstat 142, 160, 180.. i think i might be a visual learner..lol but correct me if i wrong, is this right or am i close.
thanks
q

Nordicflame,

did u build those motors in the pics

Yes we did...
And two of these....
It's been a busy winter! I'm ready to go play:ernaehrung004:

Dave

wow, I want to go and play as well. i spent the past summer on dry docks so u know i'm itching to go..:-)

am i close in post #21 because i ready to start building..

q

NordicRage
can u send me the link for the flow diagram..i tried to go to the pervious page but it's not allowing me..

q

Plug the circulating pump and drill a 1/8" hole on the thermostat. works fine on mone for 2 years now.

Mark

If you have the merc style Thermsotat housings where the water comes the the raw water pump to the Thermostat housing then out to the circ pump that should work ....not sure why you would even need the 1/8' hole ...m

I have the EMI crossover system with thermostat and bypass. I was told to drill the hole in the thermostat to relieve water pressure. Also supposed to decrease temp fluctuation. I drilled the hole and everything works perfect.

thanks for all the input thus far..

Next question what would be a good option for an electric fuel pump min. 6 PSI's or would the stock one work just fine..
i was thinking of going with a Holley Blue pump

thanks

you cant run more 7-8 pounds on the carb ....your going to have to regulate it down if your running the stock MPI pump ..m

so would the Holley Blue work, the carb i have is the Holley 4150

The engine builder just got back to me and stated this.. (" You have constant flowing water to your exhaust system at all times specially when using a thermostat. If your thermostat blocks the flow of water and does not bypass for the exhaust cooling you need to drill the manifold and bring water above the thermostat. If the housing has water to the exhaust with no restriction you need do nothing to the manifold. The bottom line is the cooling system needs water at all times, you cant have the thermostat block water off when the engine is cold")


so in other words it sounds like i don't have to drill using the Stainless Steel T Housing in the picture because it does not block the water..am i on the right track..just wanting to make sure..and i'm sorry for going back and forth with this..

cheers

Q

You are correct! You do not need to drill the manifold. Just make sure when you install the thermostat that it goes in first and then the spacer goes in below it.

Thanks,

I will keep u guys posted with the build.. :-)

Hey fellas,

which gasket am i using with the thermostat assembly the left or right. also the sender assembly temp is not fitting what should i do. the base of it is to wide.

thanks q

heres a little progress with the install. but i still need to know about the gaskets for the therm.

thanks
q