Not pumping water at idle speed

[mrtom]

Should my Forty Plus Longshaft pump water at slow/idle speed? It pumps like crazy at medium to full throttle but stops pumping when slowed down.

[5876roger]

No, I think you will find that is quite normal, advice elsewhere on the site seems to suggest that if your are running for some time at idle without water pumping then blipping the throttle every minute or so to pump water will keep the engine cool. Great little motors these 40ies.

[chris]

it is normal not to pump at idle, don't worry about damage from overheating, they just stop when they get to hot,
the 102's still pump at idle

[outboard]

Yep, that's what the usual information is regarding pumping water, however for the sake of me I can't remember who showed me a picture on the forum, I think it's our friend from Nova Scotia. What he does is, fit a small hose from the water outlet hole on the block and take it about 2/3 or 3/4 way down the shaft, what it does is create a syphon and the water runs through even at idle speed. I tried it and it works.

Gerard

[Shawn]

Found this on youtube....

http://www.youtube.com/watch?v=cfjpVoazL2Q

Shawn

[chris]

that could be the reason the 102 pumps at low speed as the water outlet is lower

[atoyot]

Here's the final version of the unit found on Youtube (mine, at least) which was first prototyped with a short piece of flexible Tygon tubing and then some semi-rigid Teflon tubing.

This version uses stainless steel and proper fittings. Note also that the exhaust tube relief holes have been plugged and smaller ones put lower on the leg. That cuts noise by a good bit, considering, though it's still very Seagull-like. The odd 90-degree fitting was an attempt at exhaust-tube water injection but I gave that up in favor of better idle cooling.... that fitting now is just an extra relief hole for all practical purposes; it's too big a hole to plug otherwise with anything I have. Perhaps a short stove bolt would do it though it adds to the mystery being there.


-ted

Please click on a thumbnail to see a larger photo...

[Hinchy1964]

Hi Ted, good work. Did you have to tap some threads into the block to accept the union? What size pipe and threads on union?
Thanks
Ian

[atoyot]

Hello Ian.

I did tap the block for the stainless steel compression fitting, which I believe is referred to as 1/4" NPT. This makes the inside passage 1/4" and the thread is around 3/8" & tapering wider as it gets turned in. The tap itself is a taper as well; just widen the original hole a little and that all basically falls into place step at a time.

The pipe is stainless, 1/4" (i.d.).



Thank you!


-Ted

[phil]

That would be 1/8 NPTx27, it is very similar to the fuel tank tap. Don't recall which drill it follows but will check.
The drill for 1/8 x27 NPT tapered is Q [.332"], for British tapered 1/8" x28 tapping drill 21/64" [.328"]