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Multiple questions on 318 refresh

D

Drfeno

Member
Hello, I recently posted a question regarding one of my motors not being able to stay running. Thanks to all who responded. The suggestions led me to the issue. I'm refitting a 1981 Silverton 31c with 318s and V drives. Both of the motors have now started and run long enough to reach operating temperature. I now have both heat exchangers removed for inspection/cleaning. I've rodded them out, and have removed some debris by flushing (not much). Since this is the first time I've had them off, I suppose I should have them checked for leakage, but they look pretty good (internally). One exchanger does have 2 tubes blocked by something that appears white as best as I can tell. I'm unwilling to try to press too hard with the rod in case these have been blocked intentionally. Also, in researching this, These can have anodes inside the seawater side. Do these just get dropped into the seawater side of the exchanger? Also, the vessel had dual stations, but once rebuilt will only have one (no more flybridge). I've read that I now need a single station temp sender due to different resistance drops with temp. Does that also apply to the oil pressure sender? I'm also curious about the location of the temp sender. There is a sender that penetrates the water pump, so I figure that's it, but there is also another device that looks like a sender that is right behind it, but in a horizontal position, it seems to penetrate the coolant tank, but I cant really tell. I would also like to flush the coolant passages in the engine, but I would think the thermostat might block that. I cannot seem to locate the thermostat housing, nothing jumps out at me as a typical flanged housing that holds a thermostat. Is it under the coolant tank? Also, on the rear of the engine, there is an oil pressure switch, and an oil pressure sender on the same manifold that's fed by a braided line. There is also another sender on this manifold that has 2 wires going to it. In looking at the wiring diagram under the engine covers, the vessel may have had the optional alarm systems. but I don't see anything on the instrument panel that would seem like indicators for alarms. Anyway, forgive my lack of familiarity with this engine, its really the first time I've dug into it in any detail.
 
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Drfeno said:
I now have both heat exchangers removed for inspection/cleaning. I've rodded them out, and have removed some debris by flushing (not much).
The sea water side of the tube bundle is accessible by average Joe.
The Ethylene Glycol side of the tube bundle is NOT easily accessible by average Joe.

One exchanger does have 2 tubes blocked by something that appears white as best as I can tell.
If they have been blocked off, it will be via silver solder... or should be.

Also, in researching this, These can have anodes inside the seawater side. Do these just get dropped into the seawater side of the exchanger?
Yes, they are to sacrifice themselves instead of your expensive copper/brass components becoming sacrificed.
In some conditions, these need to be changed more than once annually.

Also, the vessel had dual stations, but once rebuilt will only have one (no more flybridge).
I own a SDN F/B boat. You'd be hard pressed to sell me on a single station boat after having an F/B boat.
I hope that this was a good move for you.

I've read that I now need a single station temp sender due to different resistance drops with temp.
Yes, you now need single station sender units.

Does that also apply to the oil pressure sender?
Yes!

I'm also curious about the location of the temp sender. There is a sender that penetrates the water pump, so I figure that's it, but there is also another device that looks like a sender that is right behind it, but in a horizontal position, it seems to penetrate the coolant tank, but I cant really tell.
A coolant temp sender should be installed in the intake manifold, and prior to the thermostat location.
IMO, being installed the circulating pump or in the H/E would be incorrect.
The reason being.... we want to sense the coolant temperature ahead of the thermostat.... not after it.

I would also like to flush the coolant passages in the engine, but I would think the thermostat might block that.
If these are fresh engines, there should be no need to.
However, doing a flush is certainly not a problem.

I cannot seem to locate the thermostat housing, nothing jumps out at me as a typical flanged housing that holds a thermostat. Is it under the coolant tank?
Post several photos of your engines.


Also, on the rear of the engine, there is an oil pressure switch, and an oil pressure sender on the same manifold that's fed by a braided line.
The sender is for the oil pressure gauge.
If there is also a switch there, it may be for an electric fuel pump relay, or perhaps a low oil pressure alarm.

There is also another sender on this manifold that has 2 wires going to it. In looking at the wiring diagram under the engine covers, the vessel may have had the optional alarm systems. but I don't see anything on the instrument panel that would seem like indicators for alarms.
With two wires it may be for an over-temp alarm.
Click to expand...



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Thanks for the info, The 2nd temp sender I mentioned does seem to be in the intake manifold, its just tucked below the coolant tank where its difficult to see. If that is in fact the coolant temp sender, what is the one in the water pump housing? The motors are new (reman) longblocks purchased by the previous owner. One has about 50 hours on it, and the other about 30. The coolant came out looking good, very clear, no signs of oil or other contamination. As for the 3rd device on the oil pressure manifold, you're probably right, its probably an oil temperature alarm. I'll try to post some pictures of the motor
 
Drfeno said:
As for the 3rd device on the oil pressure manifold, you're probably right, its probably an oil temperature alarm.
Click to expand...
An oil temp alarm sender would most likely be fit into the oil pan.
A port on the engine may not show the exact oil temp.


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OK, I looked at it some more last night, and the additional senders must be for alarms. I did take some pictures. the one below is the oil pressure senders. I labled the sender in queston "other". I ran into some issues trying to post more than one image. I also have one of the temp senders, and the coolant tank. I do believe, that the thermostat must be under the coolant tank.
 

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Hard to tell by the photos.

I'd certainly recommend that you rid this of the push-on hoses.
Either build yourself a brass manifold affair......, or find another means of connecting these into your pressurized oil system.

Or.... have some custom made higher pressure hoses made up.


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Drfeno said:
Thanks for the info, The 2nd temp sender I mentioned does seem to be in the intake manifold, its just tucked below the coolant tank where its difficult to see. If that is in fact the coolant temp sender, what is the one in the water pump housing? The motors are new (reman) longblocks purchased by the previous owner. One has about 50 hours on it, and the other about 30. The coolant came out looking good, very clear, no signs of oil or other contamination. As for the 3rd device on the oil pressure manifold, you're probably right, its probably an oil temperature alarm. I'll try to post some pictures of the motor
Click to expand...

I have a '77 Silverton with the same motors. The sender located at the circulating pump is your coolant temperature alarm. Mine is rated to alarm at 200 degrees. The one located in the manifold is the temp gauge sender.

Thanks,
JJ
 
Thanks for the info, I've owned the vessel since 2008, but took it out of the water after 2009 (had kids). Hopefully will put it in next season. Its currently in my yard, so its easy to work on. Even though the boat is completely apart now, I'm just curious how your temp alarm alerts you. I don't remember anything like that on either of the control stations. Could have been removed or modified by previous owner(s). I do remember some lights on the upper station for the V drives, but that's it. While I'm asking, is there anything I should do for V-drive maintenance? I did check the fluid levels, and they are both full, and the fluid looks good.
 
Drfeno said:
Thanks for the info, I've owned the vessel since 2008, but took it out of the water after 2009 (had kids). Hopefully will put it in next season. Its currently in my yard, so its easy to work on. Even though the boat is completely apart now, I'm just curious how your temp alarm alerts you. I don't remember anything like that on either of the control stations. Could have been removed or modified by previous owner(s). I do remember some lights on the upper station for the V drives, but that's it. While I'm asking, is there anything I should do for V-drive maintenance? I did check the fluid levels, and they are both full, and the fluid looks good.
Click to expand...

My temp and oil alarms alert by using a buzzer. The buzzer is located behind the lower helm (you can't see it). Mine is accessed by removing a wall panel in head.

I'm assuming your head is forward the lower helm on the starboard side, like mine? If so, there should be a small panel you can remove to access the wiring and instruments for the lower helm.

The only v-drive maintenance I've done is changing the fluid. Make sure you drain the fluid from both of the v-drive housings: the main drive housing and the smaller "knuckle" housing where the prop shaft couples too. There's a 1/4" drain plug down low on the port side.

Thanks,
JJ
 
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