Mercruiser Figure 8 waterhose question

[novausc]

I bought an 82 Chris Craft scorpion about 2 years ago. I had to have some work done to the engine and now it runs pretty good. I have seen alot of pictures of similar setups but I have yet to see one with this figure 8 hose setup on top of the block. Can anyone tell me if this is where someone jury rigged something or am I missing something? It was like this before I had the work done and the mechanic said he didn't know why it was like this.

 

[EMC 1810SS]

Re: Mercruiser Figure 8 waterhose question

Thats really odd. I have always seen the hoses come off the thermostat houseing to the Manifolds, not back into the intake.

 

[novausc]

Re: Mercruiser Figure 8 waterhose question

I am wondering if this was done because the manifolds are leaking somewhere. Can anyone tell me if this "bypass" is damaging to the engine in anyway?

 

[haulnazz15]

Re: Mercruiser Figure 8 waterhose question

Are there any cooling lines going to the risers/manifolds? How does water get out of the boat? Unless they have some hoses hidden or "t'd" somewhere, your manifolds/risers appear to be running without water cooling them. That means melted exhaust shutters/rubber parts. I suppose you cold have hoses entering from the rear of the manifolds, but I don't know why would you run it that way.

 

[Brentathon]

Re: Mercruiser Figure 8 waterhose question

I would say, it's more like the infinity symbol.
I would get the manual, and confirm the correct plumbing, as hoses bent in that fashion just doesn't seem right......the one on the left is almost collapsed at the bend. Let us know what you find.

 

[Brentathon]

Re: Mercruiser Figure 8 waterhose question

Your T-stat housing has a pipe plug in the spot where normally there would be the brass Tee (with check balls) which feeds the elbows........or, at least that's how I know it on raw water cooled setups.

 

[haulnazz15]

Re: Mercruiser Figure 8 waterhose question

It looks like they eliminated the riser cooling and are routing all cooling through one hose probably t'd to each manifold on the bottom. While this method works okay, I don't see much benefit in it. My 351w runs all cooling through the manifolds and out through the risers, but I don't have a thermostat manifold which would allow direct cooling water to go to the risers. I'd say just run the hoses they way the diagram that Bubba provided shows.

It seems like he has an extra fitting/hose behind the "t" for the exhaust elbows. That one has me puzzled compared to the Merc 898 diagram.

 

[Don S]

Re: Mercruiser Figure 8 waterhose question

What happened, was the manifolds and risers were converted from the old log style manifold which had the type of thermostat housing shown in the picture. With the center rise type manifolds and risers, it needs to be setup like the diagram bubba posted.
Your engine has the wrong Tstat housing for those manifolds.
The way it's setup now, the thermostat is bypassed.
Here is a diagram of how your cooling system was originally plumbed. Compare the thermostat housings.

 

[Bondo]

Re: Mercruiser Figure 8 waterhose question

Can anyone tell me if this is where someone jury rigged something or

Ayuh,... That certainly is a Cobb Job, for Sure...

 

[Don S]

Re: Mercruiser Figure 8 waterhose question

I did notice that, but figured it must be plumbed to the bottom of the manifold since he said it seemed to run ok, and didn't mention any overheat of any kind.
Either way, he still has to replace the thermostat housing, or the manifolds. What he has pictured will not work right.

 

[haulnazz15]

Re: Mercruiser Figure 8 waterhose question

I did notice that, but figured it must be plumbed to the bottom of the manifold since he said it seemed to run ok, and didn't mention any overheat of any kind.
Either way, he still has to replace the thermostat housing, or the manifolds. What he has pictured will not work right.

I agree. That's what I assumed as well. I figured they must have a T in the hose underneathe somewhere in order to feed both manifolds off of one hose. Either way, not a good setup. His mechanic should be strung up, lol.

 

[novausc]

Re: Mercruiser Figure 8 waterhose question

You guys have given me a lot to think about here. I am not a boat mechanic by any stretch of the imagination. I am fairly good with older automobiles so I do know how to turn a wrench. I will get some better pictures of the plumbing to see if I can determine how it's plumbed. I was rather concerned myself that without and outlet the water can't be flowing but I can see the water coming out of the exhaust elbow at the outboard when it's tilted up and I have a water muff on it so it has to be flowing somehow. The really scary thing is the boat runs fine. WOT is 4000 rpms and it gets on plane around 2300. I've put about 30 hours on it since it was rebuilt but I do have a strange problem with what I believe is vapor lock on really hot days. I wonder now if the two issues are related. I will post back what I find.

 

[Don S]

Re: Mercruiser Figure 8 waterhose question

I can see the water coming out of the exhaust elbow at the outboard when it's tilted up

I sure hope you aren't running the engine with it tilted all the way up ????????????

 

[Bondo]

Re: Mercruiser Figure 8 waterhose question

The really scary thing is the boat runs fine. WOT is 4000 rpms and it gets on plane around 2300.

Ayuh,... And yer Lugging the motor,...

Rpms at Wot should be 300 to 600 rpms Higher...

 

[novausc]

Re: Mercruiser Figure 8 waterhose question

OK, sorry it took so long for this information. I've been so busy I haven't been able to even think about my boat. I have pictures that may shed more light on how it's connected. It looks like a single water hose comes off the top and goes to each manifold in the bottom center. There are forward and rear plugs in the manifolds so I'm not sure why its like this. I would need some of your expertise to enlighten me. These manifiolds don't look like the ones in the diagram for the manual so I assume they are from another engine since they do have the mercruiser stamp on them. I also got a shot of the plate that has my serial on it as well as the WOT settings. I'm a little confused since it says 3800~4200 for WOT. Shouldn't that mean my 4000 WOT is right in the middle and in the best place? Why should it be 300 to 600 rpms higher? As always, any help would be greatly appreciated. If there's any more information needed please let me know. I can take pictures all day if it helps me make my boat run better without damaging something.

 

[novausc]

Re: Mercruiser Figure 8 waterhose question

Can someone doublecheck my "math" on this. If I follow Don S.'s diagram as the setup I have for my thermostat houseing with Bubba's setup for my manifolds in his diagram then the hoses connected to the exhaust manifolds are water inlets not outlets meaning their trying to draw water from the manifolds,......How is this working?

 

[Bondo]

Re: Mercruiser Figure 8 waterhose question

Can someone doublecheck my "math" on this. If I follow Don S.'s diagram as the setup I have for my thermostat houseing with Bubba's setup for my manifolds in his diagram then the hoses connected to the exhaust manifolds are water inlets not outlets meaning their trying to draw water from the manifolds,......How is this working?

Ayuh,... The problem you've got is whomever replaced the old log exhaust manifolds, Should have also changed the T-stat housing to match the set-up...
In other words, those hoses are nothing but a Cobb Job, 'n a pretty poor 1 at that...

I stand corrected on yer rpms at wot,...
You have the old 2bbl. carbed motor...

 

[novausc]

Re: Mercruiser Figure 8 waterhose question

I am confused. Don and I both posted the diagram on how it is supposed to be. Are you looking for another way to do it wrong?

I'm not sure where your confusion is, I am trying to make sure that I don't make it worse. My setup appears to be a hybrid between your diagram and Don's. I think all I need to do at this point is to replace the thermostat housing for an 898R and connect everything according to your diagram.

 

[dubs283]

Re: Mercruiser Figure 8 waterhose question

hybrid...yeah, thats a nice way of saying it

someone installed new style manifolds on the engine that was orginally equipped with log style manifolds, probably got a deal on some used ones

in any case, they failed to install the t-stat housing that goes with that style cooling system

what you need to do is install the proper style t-stat housing that is compatible with the manifolds you now have

if you look at both diagrams closely you will see the definite differences and what needs to be done to correct your issue

 

[Bondo]

Re: Mercruiser Figure 8 waterhose question

I'm not sure where your confusion is, I am trying to make sure that I don't make it worse. My setup appears to be a hybrid between your diagram and Don's. I think all I need to do at this point is to replace the thermostat housing for an 898R and connect everything according to your diagram.

Ayuh,... Your's used to look like Don's, 'n you need to finish makin' it look like Bubba's....