40 hp evinrude 1974 40455s extremely loud exhaust

[buddhapi]

this is the second of these old 1974 40hp Evinrudes I've worked on this year, and this one has much louder exhaust than the first one I worked on. I'm talking extremely loud....deafening!! any idea what I can do to tone this one down? is there something wrong with it internally? I've rebuilt the lower unit, carburetor, and replaced the reed plate gaskets.

 

[jimmbo]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

Are you running it in the water, or hooked up to garden hose?

 

[buddhapi]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

yes, I'm running it in a big tub of water. it does seem like a lot of bubbling out the prop. even throwing water out in neutral.

 

[boobie]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

How does it sound on the lake ??

 

[buddhapi]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

I don't dare put this thing on the lake. noise ordinances.

 

[buddhapi]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

More to this I think. The whole bubbling out the prop thing....it's like taking a straw and blowing into a glass of milk! when I pulled this lower unit off initially weeks ago, you could see there was a lot of heat with the baked on gunk on the shift shaft and water tube, which I scraped off with a butcher knife. Is there any way this 2 cylinder motor could be running backwards? did all Evinrude starters spin the same direction? the owner of this engine has been having issues with performance since he bought it a few years ago, and just isn't able to use it any longer the way it is. I checked the contact points today and the gap is right on .020, and both cylinders are at 118 psi. I know it's getting late, but any thoughts?

 

[jimmbo]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

These are internal combustion engines, they make noise. The under water exhaust shuts it up as good as any muffler. It idle there is the exhaust relief along the back of the leg where ther water sprays out. At higher speeds the water flow through will block off the idle relief forcing all the exhaust out underwater. A 1970 40hp does not discharge its exhaust thru the prop but through a seperate outlet behind the prop. There is an access cover for the shift linkage on the midsection. If missing, loose or a leaky gasket the exhaust could be leaking there.

 

[buddhapi]

Re: 40 hp evinrude 1974 40455s extremely loud exhaust

okay, I see now. the exhaust exits out above the prop. that would be loud. I'm going to throw it on my test boat and get it out next week for a test run. I cleaned and reset the points, and it seems to have lot's of power and it's pumping water. I will post on here my results. it still seems louder than the last one I worked on. hmmmm....