Couple old evenrude questions

[putback]

I'm just finishing up a '62 Lark 40hp. I'd like a temperature gauge on it. Nothing I've ever done, any advice. Especially how / where to install a sending unit? 2nd question. Have a donor engine with the add on rubber fins attached to the cav plate,[ what do you call those things]. Anyway what purpose do they serve and would they be of any use on this 40 hp Lark pushing a 1960 15.5 ft alum hull?

 

[rotus623]

I call those fins whale tails. They are actually called hydrofoils. They CAN help to plane the boat out and prevent porpoising, at the cost of added drag and maybe a loss of 2-3mph. I don't like them as I feel they are making up for a flaw elsewhere in the setup (too small of a motor, bad weight distribution, waterlogged boat etc.) but i would leave it on there and run it, then take it off and compare the differences.

As for temp gauge, if you want that or a water pressure gauge you will likely have to drill out and tap threads into the water jacket for either a temp sender or a water pressure gauge outlet.

On an older motor like that I would just put in a new waterpump and see what temp she runs at.

 

[stinkfoot]

Gets you out of the hole quicker. Adds drag. It's only 4 screws but then you'll have holes in your cavitation plate which guess what? ....adds drag if you don't end up using the foil. I have two lower prop units for my 40 jet one with a hydrofoil and one without. Planning on a little experiment this summer to see what's what....

 

[putback]

Ok, sounds like a solution looking for a problem. I won't bore holes in a perfectly fine cav plate unless I need to, thanks. As for the temp sending unit for a gauge I'm not to keen on boring & taping the water jacket. Would a brass T in the rubber water line that runs through the auto choke work?

 

[rotus623]

What rubber line are you talking about? Does this motor have a telltale?

 

[rotus623]

Here's a good read on retro fitting a telltale. I'd start there and if you still need more assurance you could tap a Y into the line and run a water pressure gauge to the dash. https://forums.iboats.com/forum/engine-repair-and-maintenance/engine-frequently-asked-questions-faq/228380-johnson-evinrude-adding-a-tell-tale

 

[stinkfoot]

You can buy a no-drill hydrofoilhttps://www.defender.com/product.jsp?path=-1|215570|1825671|2331350&id=2200321 but better IMO to fix the issue properly.

 

[putback]

Here's a good read on retro fitting a telltale. I'd start there and if you still need more assurance you could tap a Y into the line and run a water pressure gauge to the dash. https://forums.iboats.com/forum/engine-repair-and-maintenance/engine-frequently-asked-questions-faq/228380-johnson-evinrude-adding-a-tell-tale

No telltale on this engine, that concerns me. Don't want to risk an over heat. That link helps a lot, thanks. The rubber hose to the auto choke is as follows. Fitting into water jacket #1 cly [top] near head. Rubber hose attaches goes to auto choke controll housing, exits fitting on choke controll housing, rubber hose goes to base of engine and out. I'm thinking I can use this circut to do both. A brass tee at the #1 cyl to accept a temp sending unit to an in dash temp gauge. Then another brass Tee at the engine base / exit for a telltale. Question is will that telltale affect pressure and flow?