Over Heating and Confused..

[GunHoInc]

Yep, it's mE again.

To refresh your memory I have a:

1986 Mercruiser 5.7. (Brand new) with an Alpha 1 outdrive
Raw water cooled.

I had it out this weekend, and it runs great below the 4000 rpm range(Temp below 170), but when I open it wide open it over heats (temp above 200-220), and I have to slow down and let it cool off. I asked the guy at my Marina and he sold me this new water neck kit.

(Sierra 18-1989)

New water neck:

Old water neck:

Is this kit ok? I was told to plug off the hoses to the risers and now my risers seem pretty warm. But the engine does seem to run cooler. I also noticed on the old water neck there wasn't any sort of check valve in the "T". Isn't there supposed to be one in there?

I havn't tested it on the water yet but will hopefully this week.

dAvE

 

[Don S]

Re: Over Heating and Confused..

Which setup did you have when it overheated? the system in the top or bottom pick above?????

 

[GunHoInc]

Re: Over Heating and Confused..

The bottom pick is the setup that over heated at wide open throttle. It did not have a check valve in the "T". Not sure if it was supposed to!?.

Havnt tested the new setup in the first pic yet. The motor did run cooler on the hose and ears, but the risers are pretty warm now as the hoses to the risers are now gone with this setup. Is the new setup in the top pick a good setup? Or am I headed on the wrong direction and wasteing more ca$h!?.

dAvE

 

[Don S]

Re: Over Heating and Confused..

I'm gonna have to think about this one for a while. Something is missing here.
What about the raw water pump and impeller has it been checked since the hoses were turned aroiund to the right spots?.
What about the thermostat in the old system, did it work?
What gaskets are between the manifolds and risers?

I think it's a real poor idea for your mechanic to just throw a new style thermostat housing at you and say that is why it overheats.
The old system worked for many years, why not now?

 

[sebago_kid]

Re: Over Heating and Confused..

.... and no water to the risers?
I don't get it.

 

[GunHoInc]

Re: Over Heating and Confused..

I'm thinking that there was supposed to be a check valve in the "T" of the old water neck to even out the flow of water through the system and it might have gone bad and someone pulled it. The shop said this was the recomended replacement. It's suposed to send all the water flow up through the exhaust manifolds and out the risers when the engine reaches temp. He said the risers will be hotter but not hot enough to damage the rubber boots.

dAvE

 

[GunHoInc]

Re: Over Heating and Confused..

I searched the web for info on this type setup but nothing turned up showing a pic or an install diagram. I'm going to try Sierra and see if they have a website with more info. I think I'm going to have to actually put it in the water to find out if it works or not. Unfortunatly rain all week is our forcast.

On the box it says it is a replacement water neck for mercruiser 8790A4, and 861006A1.

dAvE

 

[Don S]

Re: Over Heating and Confused..

Read this service bulletin about the type of riser/manifold gaskets that you need with the new tstat housing.
http://www.boatfix.com/merc/Bullet/99/99_10.pdf
Since it's already installed, no since going back at this point.

Are you sure the raw water pump and impeller are ok? if not, you can change thermostat housings forevery and still overheat.

 

[JustJason]

Re: Over Heating and Confused..

Another thing that needs a good looking at would be the water pocket seal in the upper unit of the outdrive. When they go they will either leak water at hi rpm or suck air. Both of which would cause a high rpm overheat.

 

[GunHoInc]

Re: Over Heating and Confused..

Yes the pump and impeller are good. Water flow seems fine. Will the new riser gaskets change the water flow?

I do still have my old parts. I might take them to west marine and see of there is anything wrong with them. I sent an e mail to sierra to find out more info and to see if they have a diagram. Thermostat is also new and works just like the old one I replaced.

About where is the high water pocket seal located in the outdrive!?.

 

[ziggy]

Re: Over Heating and Confused..

About where is the high water pocket seal located in the outdrive!?.

it where you stick the copper water pipe into in the upper for mating with the waterpump in the lower that has the guide tube on it. its the other female connection between upper and lower. not the water pump end in the lower, but the waterpocket cover in the upper.

be real careful with them 4 ss 1/4-20 bolts that hold this cover on. they are prone to breaking off. then ya'll be in real trouble if ya break one off... i believe what jj says could be true for a possible overheat reason. i've been told that too. i also found mine leaking too. the way i found the leak was having the lower off and flushing backwards with a hose towards the drive. i found water leaking at the gasket, in my case, probably from an overheat that melted (distorted) the waterpocket cover. yes, i messed with the bolts. which is how i can assure you that they break off real easy... hope that aint your problem... fwiw. i have read at least one fella hear that got away with removing these bolts on a waterpocket cover. but i've read more about them breaking, than being successful...

item #43 in s/m #6, pp3A10 is the waterpocket cover

 

[GunHoInc]

Re: Over Heating and Confused..

I'm going to try and do a test run this week. If it runs hot at high rpm then it must be in the water seal on the impeller like stated. If that's the case I'll pull the alpha 1 apart and change out the seals. They just replaced the impeller and may have missed something.

dAvE

 

[JustJason]

Re: Over Heating and Confused..

http://www.mercruiserparts.com/Show_pictures3.asp?dnbr= 99964&ivar=IMAGES/CRUISER/99964/30067.png&inbr=2203&bnbr=80&bdesc=DRIVESHAFT+HOUSING+AND+DRIVESHAFT


Parts ## 3 and 4.

Let me just ask a question here. You bought a new 350 through a marina that installed it all and they sent you out without testing the engine?
What's the rest of this story here?

 

[Don S]

Re: Over Heating and Confused..

Yes the pump and impeller are good. Water flow seems fine.

Compared to what, did you measure or just look at it and say "That looks ok to me, "

Will the new riser gaskets change the water flow?

The PROPER gaskets will make all the difference. Read the bulletin and understand what the different gaskets do.
The wrong gaskets will cause it to overheat.

 

[GunHoInc]

Re: Over Heating and Confused..

They replaced the impeller and said the original pump was ok. They test drove it but didn't run it at full throttle very long as I was there on the test run. The test run was on the river in a no wake zone near my house.

dAvE

 

[GunHoInc]

Re: Over Heating and Confused..

The more I think about this the more I agree with an air leak somewhere in the Alpha 1. When It over heated I felt the risers and they too were hot. This would discount the reason that the water flow was too fast to cool the engine as the shop owner said. And verify what you guys say about a high rpm air leak. I have a 140 thermostat and the running temp was just below 170. There is probably air in there and it's being enhanced at full throttle!?.

SOooo, since it's supposed to rain all week anyways, it will be a good time to get some seals and gaskets and pull the drive and take my time going through it. I'm leaning on putting the original water neck back on as I'm a stickler for "FACTORY" stuff as opposed to after market BS. (I think the new water neck looks like crap anyways)

dAvE

 

[captmello]

Re: Over Heating and Confused..

4b.
Raw water cooled engines with the bypass water from the thermostat housing going
to the fitting on the exhaust elbow and the warm water from the thermostat housing going
to the 90-degree fitting on bottom of the exhaust manifold:
Use P/N 27-863724 Gasket ? Restrictor between the exhaust manifold and the exhaust
elbow.
If the engine has 3 in. (76 mm) or 6 in. (152 mm) risers, use P/N 27-863724 Gasket ?
Restrictor between the riser and the exhaust elbow. Use P/N 27-863726 Gasket ? 4 Slot
between the exhaust manifold and riser.

This may be the part of the bulletin Don was referring to. If you're running the restrictor gasket with your new system your restricting the flow through the manifolds.

That would be my first move. I think I'd wait to pull the drive apart. Good luck too you.

 

[GunHoInc]

Re: Over Heating and Confused..

Actually today I'm going to change out the water pump so I can say that the top of the motor is 100% new. I'll wait and test drive it. If the problem persists then I'll go further.

Well that went smoothly enough. Boat motor is all back together with a new water pump and the factory water neck. Somehow I don't think the pump was the problem butat least now I'm confident with the new pump. Ill save the old one as a spare.

Is it common for the motor to get hotwhile running off a garden hose? When I reved the motor it climbed over 170. Pressure in the lines seemed low.

Thanks, dAvE

 

[GunHoInc]

Re: Over Heating and Confused..

Ok, I called another Boat repair shop and they strongly recommended not touching the water pocket cover due to those bolts breaking off. He recommended changing out the old thermostat housing with the after market style like the other guy sold me, and replaceing the riser gaskets with the recommended ones for that setup. SOoooo, I'll have to get those gaskets and start again.

dAvE :redface:

 

[cooter2506]

Re: Over Heating and Confused..

Dont you already have the new t-stat housing in place? If so just change the riser gaskets out to the proper ones. That set up is fine as long as you have correct gaskets in place.