1975 75hp Evinrude 3-Cyl - Cooling Water

[munawar]

High, I just bought a 3-cyl, 1975 75hp evinrude. I haven't put it in water yet; got to fix the floor first. When run the engine the cooling water spits out through the lower back but almost nothing from top exhaust port. Is that normal for these? I am used to 135 HP Mariner I had, that had continuous stream of water from the top. Somebody said it's called "**** tube", but I don't know and don't like the word, so please pardon the language here.

Thanks
Munawar

 

[TimT.]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

this is cool .....you're first post on a newly acquired 75' 75hp, mine too as I just bought a 75' 75hp Johnson. Anyways, no cooling water coming out of the "****" tube? This could mean the plastic tube end out you're cowling can be plugged..easy fix is to pop it out and clean with a small wire, 2 you're impeller for the pump could seriously be worn. I would take a look at that by pulling you're lower unit off and getting into your pump housing and taking a looksee at the impeller....

 

[Daviet]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

I am not sure your engine has a tell-tale indicator.
If you are talking about the two exhaust ports on the upper rear midsection, running on the hose most of the water will come out at the prop. When you put it in the water the exhaust housing will fill with water and force water out of the exhaust ports.

 

[jtexas]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

nope, no tell tale (AKA **** stream) on the '75 3-cylinder. Tim if yours has one it was added by a prior owner. There's an illustrated how-to on this forum, look in the "Engine FAQ" section.

To test your overtemp warning horn, find the temp switch at the end of a tan wire next to the thermostat housing high on the cylinder head.

Peel back the rubber sleeve (a few inches back) and touch the connector to the cylinder head (keyswitch "on"). A steady tone should sound.

Quick test of the cylinder head temp at idle: hold your fingertips against the cylinder head for a few seconds, then pull away. If you didn't leave any skin on the motor, it's not overheating.

Use only champion QL77JC4 gapped at .030
Use only fresh 87-octane gasoline in a 50:1 mix with TCW3 certified oil.
Change the gear oil annually and the water pump impeller every couple years.

Temp switch location ('79 model with 'stat housing removed):

 

[joey nathan]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

As I understand it, the exhaust is primarily through the hub on this engine.

Once you get underway, the two poppet valves will open against the springs and water will then exit out the two holes higher up on the housing. But you have to be going along at or near WOT for this to occur and not while on the muffs.

 

[jtexas]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

As I understand it, the exhaust is primarily through the hub on this engine.

Once you get underway, the two poppet valves will open against the springs and water will then exit out the two holes higher up on the housing. But you have to be going along at or near WOT for this to occur and not while on the muffs.

The exhaust is through the hub.

When the boat is stationary or moving slowly, pressure on the underwater exhaust is high, and some exhaust is vented through the "exhaust relief ports" on the back of the motor. Your motor would have difficulty starting and idling with those relief ports submerged or otherwise blocked.

Running on muffs, and when the boat is moving fast, there is no backpressure on the underwater exhaust, so none or very little exits the relief ports; they are irrelevant at high speed.

The two poppet valves have nothing whatsoever to do with exhaust. They open when water pressure rises (e.g. RPMs and boat speed increase), to allow better water circulation through the powerhead. They are irrelevant at low speed.

 

[munawar]

Re: 1975 75hp Evinrude 3-Cyl - Cooling Water

Thank you all so very much for your suggestions. It doesn't really have the tube. With ear muffs at least the water comes out from a hole opposite to props in addition to the prop. So I'll finish fiberglassing the floor then put it in water and try to remember to shoot some pics for you all.

I really do appreciate all the help.

Kind Regards,
Munawar