Evinrude 3hp Hot Exhaust Plate..

[frustratedboater]

Greetings all,
I routinely fired up one of my recent restorations, an Evinrude Lightwin, 3hp, and noticed that the exhaust plate had discolored the fresh paint job.

Last winter I had the block torn down I had made sure that all the cooling ports, water channels, were clear, really taking my time on this. The impeller is fresh and everything is to spec!

One test I did perform was taking the flush plug out and ran it to see the pumping action if any. It shot a 6'-7' stream out! So, the pressures there! On the other hand the exiting water spray was nothing to be impressed with. Just a little spray out the plate.

Do these engines run that warm, to discolor the plate (ran about 3-4 minutes to set the idle)? Should there be more of a discharge of water out the plate?

Need your advice on this one...

~FB~

 

[tx1961whaler]

Re: Evinrude 3hp Hot Exhaust Plate..

I have a couple of late 1950's 3's. There is not much that comes out of the exhaust diverter port on the leg; just enough spray to let you know it's there. The exit water coming out of it isn't really hot on mine.
I haven't stuck my hand on the exhaust plate to see how hot it gets. I'd assume it gets pretty hot, since the pistons are right there under the plate.

 

[DJ]

Re: Evinrude 3hp Hot Exhaust Plate..

You shouldn't burn the paint off.

My 3HP and 4HP engines have both had clogs under the powerhead where the block meets the midsection.

 

[F_R]

Re: Evinrude 3hp Hot Exhaust Plate..

Sorry, I have to disagree. The 3hp exhaust plate gets scorching hot. There is fire on the other side of it and it is only water cooled along the forward edge. The rest of it is an eighth of an inch of aluminum between you and an inferno. You don't want to be touching it!

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

I agree with you on the heat. When I was clearing the ports channels in the block, I took special attention to the cooling as I saw the plate pretty scorched. I took a long drill (same bore as the channelway) and ran it down across the top of the block, that comes up the right side and over,towards the plate area. All in hopes to clear any salt, 'gunge', or any corrosion that may have swelled, or pervented the passage of water.

There's something that's not right though... There should be an effective way to increase the flow of water throughout the block. Would opening the head gasket holes allowing more penetration through help? I still think there's some kind of resistance, or blockage...

I'm not loosing sleep over it. Yet!

~FB~

 

[Chinewalker]

Re: Evinrude 3hp Hot Exhaust Plate..

The plate is SUPPOSED to get hot. If the cylinder head is getting sizzling hot, then you have a problem, but the exhaust plate getting hot is not an issue...
- Scott

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

Thanks Chinewalker, I did notice that the pistons has slightly groved sides than the other, but nothing major, and everything calibrated up fine. I was just concerned and didn't want to run the motor hot, and run into problems later. The motors' got some history and want to be sure that everything is tip top and running smooth!

~FB~

 

[R.Johnson]

Re: Evinrude 3hp Hot Exhaust Plate..

I have one of these 3 hp engine's. Running it on a 14 ft jon boat at idle with someone on the front seat in choppy water, it would some time lose prime for a short period of time. At the top of the cylinder head you will find a core plug. I removed this core plug, and tapped the hole 1/8" pipe thread, you don't have to drill out the hole to do this. I then screwed in a plastic elbow as used on any over-board indicator. You will have to grind a little off the top of the elbow to clear the mag plate. Attach the rubber hose and run it out the bottom of the cowling. This will give you an over-board indicator, and you can tell at a glance the engine is getting water. This also solved the losing prime issue. The 3 hp does not have a double, water cooled plate like the bigger engines, so it get's to hot to touch, or will discolor paint.

 

[DJ]

Re: Evinrude 3hp Hot Exhaust Plate..

Sorry, I have to disagree. The 3hp exhaust plate gets scorching hot. There is fire on the other side of it and it is only water cooled along the forward edge. The rest of it is an eighth of an inch of aluminum between you and an inferno. You don't want to be touching it!

Hmmmm. I guess my 3 and 4 HP engines are defective. They still have the original paint on them.

 

[F_R]

Re: Evinrude 3hp Hot Exhaust Plate..

Nice paint.

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

R.JOHNSON:
When you say "lose prime", I'm sure you are refering to water pump 'prime'? Interesting concept on the over-board indicator. From my experience, those little 2's and 3's don't pump as much volume as the vintage 7.5's, 10's, ....30's and 35's. I'm always cautious on the little ones.

How deep does this core plug go? Is it solid aluminum all the way through? I'm trying to remember on my head there was a mid flattened section on the top center of the cyl head.

~FB~

 

[R.Johnson]

Re: Evinrude 3hp Hot Exhaust Plate..

The core plug is the same thickness as the plug's used on a carb. You can drill, or punch a hole thru it, and it will pry right out. As I said before, you can tap right down this hole with a 1/8" pipe tap without drilling out the hole. On these little engine's you only get a little spray, or mist out the exhaust leg. You almost have to reach back to feel if it is pumping. I used the same plastiic elbow as used on the bigger engines with tell-tale. You have to grind a little off the top of the elbow, and screw it all the way down to clear the mag plate. I run the hose down the right, back side of the engine, and held it in place with a tie strap. I drilled about a 1/16 hole thru a brass shear pin to act as a restrictor, and put this in the end of the hose. I was surprised at how much water pressure I had at the tell-tale when I was done. Tapping water off the top of the head seam's to also make the engine run cooler. I did this two both of our 3 hp motors', a 1957 Johnson, and a 1968 folding model. Never had a problem with either.

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

Wow! That's fascinating... I don't remember my head having an aluminum plug cap on it to pry out. Would it be possible to insert a pic of what you're talking about, or email it to me? I'd love to see it. I can understand the concept and how you'd run the line, but I would have to look again at my head for the plate you're speaking of. It is on the head you're tapping?

~FB~

 

[R.Johnson]

Re: Evinrude 3hp Hot Exhaust Plate..

Sorry! I was way off on this. The plug is on the right side of the block just forward of the cylinder head. It look's like a tube cast right into the block, and will have a small plug out at a right angle. It's the top plug you remove. It's been so long since a done this, I was thinking it was on the head.

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

I'll have to take a peek at mine today... very curious

~FB~

 

[R.Johnson]

Re: Evinrude 3hp Hot Exhaust Plate..

The last modification I did was on a 1955, 7 1/2. That did have the core plug in the head. Another reason I put the tell-tale on the 3 hp, the engine has a shrould all around, it is hard to tell by feel how hot it is running. You don't need a tell-tale, I'm just more comfortable with it.

 

[frustratedboater]

Re: Evinrude 3hp Hot Exhaust Plate..

True, I was questioning the 3hp just to ensure its' getting the water, but I also have a #7522, 57', 7.5, that I'm thinking of. Purchased that last year (drove 350 miles to pick it up) that I would like to go over it this winter. I just want to make sure my engines are running cool...

~FB~

 

[R.Johnson]

Re: Evinrude 3hp Hot Exhaust Plate..

Take a look at your 7 1/2, that's real easy to do.