Hi firstly can i apologies if this subject has been discussed before.I have a forty plus that im in the process of rebuilding.When running in a tank with or without a prop attached hardly any water comes out of the hole in the block.I have replaced the impeller, have tried fitting it both ways around,i have taken the water feed pipe off and cleaned it and reconnected it to the block with ptfe tape. I have connected a hose to the bottom of the pipe and also backflushed the engine and the water flows fine,but as soon as its running i get hardly any water.I think the problem maybe in where the gearbox meets the pump housing,the original impeller had dropped down the shaft and wrecked the gasket and the impeller,so i replaced the impeller with a new one and replaced the gasket with another off another 40 plus which was in good condition.On inspection i found that the original gasket was slightly thicker than the one i replaced and im thinking that this could be the reason for the lack of cooling.
Has anyone else had this problem or could help me solve the mystery??
Thanks Steve
Forty plus annoying cooling problem
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Ian Malcolm
- Posts: 108
- Joined: Thu Mar 30, 2006 11:42 am
- Location: London, ENGLAND
You have got the water level between the flat top of the foot and the pinch bolt? If its too low, it will NEVER pump properly when stationary.or going slow.
Dont expect miracles, it doesnt need a lot of flow at low revs. Its fine if it comes in spurts a few seconds apart. As long as it isn't steaming you wont do any damage but the side of the block should remain cool enough to keep your hand on. OTOH from about 1/3 throttle up you should have a nice continuous stream.
Check the water tube is a good fit into the socket in the foot. If it leaks here it may not be able to get water up to the block at low revs. A few wraps of ptfe tape and a smear of NON-HARDENING gasket compound (you DONT want to use anything that sets too well as you may need to get it apart again) can do wonders for the slow speed cooling.
As I remember the plastic impeller has one end open to the vanes and the other end is a disk. The open end *MUST* face the hole in the gasket and you dont want much clearence at all between it and the gasket. Anything over 1/16" is too much. OTOH it must NOT touch with you pushing down on the driveshaft while turning the prop over by hand and you want a little margin for gasket swelling and wear that might reduce the clearance. If its the wrong way up or has excessive clearance it wont pump well at all..
Many people have reported their seagulls letting them down because the driveshaft end has split due to rust pitting so while you've got it apart, clean off all the rust inside and out from the driveshaft, and give it a THIN coat of a good zinc anti-rust primer. Its best to reinstall the impeller when the primer is touch dry but before it hardens. Touch up the paint you scrape off pushing the impeller on after you've set the correct clearance.. Paint the inside of the driveshaft thoroughly as well.
Dont expect miracles, it doesnt need a lot of flow at low revs. Its fine if it comes in spurts a few seconds apart. As long as it isn't steaming you wont do any damage but the side of the block should remain cool enough to keep your hand on. OTOH from about 1/3 throttle up you should have a nice continuous stream.
Check the water tube is a good fit into the socket in the foot. If it leaks here it may not be able to get water up to the block at low revs. A few wraps of ptfe tape and a smear of NON-HARDENING gasket compound (you DONT want to use anything that sets too well as you may need to get it apart again) can do wonders for the slow speed cooling.
As I remember the plastic impeller has one end open to the vanes and the other end is a disk. The open end *MUST* face the hole in the gasket and you dont want much clearence at all between it and the gasket. Anything over 1/16" is too much. OTOH it must NOT touch with you pushing down on the driveshaft while turning the prop over by hand and you want a little margin for gasket swelling and wear that might reduce the clearance. If its the wrong way up or has excessive clearance it wont pump well at all..
Many people have reported their seagulls letting them down because the driveshaft end has split due to rust pitting so while you've got it apart, clean off all the rust inside and out from the driveshaft, and give it a THIN coat of a good zinc anti-rust primer. Its best to reinstall the impeller when the primer is touch dry but before it hardens. Touch up the paint you scrape off pushing the impeller on after you've set the correct clearance.. Paint the inside of the driveshaft thoroughly as well.
It would be worth checking the mating surfaces of the water pump housing and top of the gearbox.They must be perfectly flat or the joint will leak as the two fixing screws are forward of the chamber which feeds the water tube to the cylinder and a leaking joint here will result in poor water flow.
Seagull must have recognised this as a potential problem as they make a point of referring to it in their service sheets.
Also,have you checked that the water inlet slots at the front of the gearbox are clear?
The water pump impellor should be fitted with the disc uppermost,they are usually marked "top" if you look carefully.
Hope this helps.
Seagull must have recognised this as a potential problem as they make a point of referring to it in their service sheets.
Also,have you checked that the water inlet slots at the front of the gearbox are clear?
The water pump impellor should be fitted with the disc uppermost,they are usually marked "top" if you look carefully.
Hope this helps.
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Ian Malcolm
- Posts: 108
- Joined: Thu Mar 30, 2006 11:42 am
- Location: London, ENGLAND
I'd try a fairly thin bead of orange silicone RTV gasket goop round the waterpump housing on both sides of the gasket first. If the castings are badly pitted but the gasket is in good condition, best to clean them well with a wire brush then carb cleaner or other oil free quick drying solvent and lightly oil the gasket so you can get it apart again. If the gasket is in poor condition, but the castings are good, change the gasket!. (or oil the castings and put the RTV on a carefully cleaned and abraded gasket).
Thinking about it- you said you took the gasket from another engine - bet its not flat and the castings were NOT machined accurately round the edges so old gaskets are NOT interchangable (the edge of a slightly wider bit of your casting will be on the ridge left by the edge of the old casting holding the joint open)
It may be helpfull to put engineers blue (or slow drying paint) on a flat piece of glass and test the casting face for flatness. It could just be a small 'ding' on the edge that could easily be stoned flat. When you've got it pretty close, you can lap them to get them as flat as your reference surface, but care is required to avoid developing a 'crown'
Thinking about it- you said you took the gasket from another engine - bet its not flat and the castings were NOT machined accurately round the edges so old gaskets are NOT interchangable (the edge of a slightly wider bit of your casting will be on the ridge left by the edge of the old casting holding the joint open)
It may be helpfull to put engineers blue (or slow drying paint) on a flat piece of glass and test the casting face for flatness. It could just be a small 'ding' on the edge that could easily be stoned flat. When you've got it pretty close, you can lap them to get them as flat as your reference surface, but care is required to avoid developing a 'crown'
Hello thanks for all your suggestions,i have now finally cured the problem by re-tapping the gearbox to pumphousing threads and putting in some larger diameter studs.The gearbox is now held secure by some external bolts,the extra torque i can now put on the bolts mean i have a better seal on the pump housing.I know its not exactly as seagull meant it but at least its running fine now.Thanks again
Steve
Steve