Logo
FULL SITE MENU

Evinrude powerdown

R

raybur

New member
"I have a major powerloss with

"I have a major powerloss with my evinrude 55 hp. It has a new stator and rectifier. During electrical work at the shop, I was told about a powerloss in one of the cyliders. I was told it could be a blown gasket or damaged reeds. This was when I bought the motor and it so overpowers my small runabout, the powerloss was not relevent. Then sudenly it went down to maybe 25 hp. The boat would barely make it onto plane. Now it bothers me alot more. It now has new spark plugs, it gained maybe a couple horsepower, I pulled the spark plugs (individually) and the lower cylinder has less power than the top one. when I pulled the plugs, I got zapped, so I think the electrical system is working, unless the timing is off. Could it still be electrical; the only things not replaced are the powerpack and coils. Do I need to take off the flywheel to get to the reeds? It takes a special tool. Are there any more special tools I will need? thanks."
 
"What is the compression of ea

"What is the compression of each cylinder? With the spark plugs removed, the spark at cranking speed should jump a 7/16" gap. Does it?"
 
"I pulled the carberaters and

"I pulled the carberaters and I found a 3/4 rubber bushing logged in the reeds. I have no idea where this thing came from. I am still losing compression in the lower cylinder. Could it be piston rings? I don't want to remove all elecrical to get into the cyliders, as there are so many wires I might get confused. I shone a light through the crank shaft and the cylinder walls look very smooth, but I don't really know what to look for, and if they were scored I think they would be on the other side of the piston, were I can't see. Are bad piston rings the only way to lose compression? Should I commit to taking my whole motor apart to change them or could it be something else? Thanks"
 
sounds like some kind of gaske

sounds like some kind of gasket got sucked in.
have you done a compression test ? what are the readings?scoring could be seen from either side.
have you tried to run it after the rubber piece
was removed?
 
"I'm waiting for gaskets i

"I'm waiting for gaskets in the mail, then I will have compression test. I took off the cylider head and the pistons have the same fit (a little play; maybe 1/64th inch) The cylinder walls are absolutely perfectly smooth. The reeds and carburators are also perfectly clean, It is difficult for me to believe this motor is 33 years old. If there is no scoring;even that the two carbs and reeds are joined in the crank case; the lower blocked reed must have transfered lower air pressure to the cylider across from it simply because it is a straight shot across the crank case. Does this make sense as the only other thing I can think of is one bad coil or can the powerpack disrupt the lower cylinder only?
My boat is small but heavy. It is a 12 ft. fiberglass deep V runabout. Before the problem, I was getting 38 mph. Prop is 12 by 17 aluminum 3 blade. Can this engine be modified for more power? Would that be a bad idea? I have heard boyeson reeds increase idle and midrange, I will install these later. I'm looking for top end. Also what rpm should I aim for when wide open? Thanks much."
 
"the power pack can drop a cyl

"the power pack can drop a cyl/when they go.
no mods needed thats pushing all it has if you do anything to it ,it will only shorten the life
of the engine and cost you more to run it.
5500 max rpm no higher,38 on your unit sounds good,i do not think you can get much faster than that."
 
"Well, here's how it goes.

"Well, here's how it goes. I replaced the head gasket and most other gaskets, both cylinders have a lot of compression, I can tell by how hard it is to manual start and the starter strains turning the engine over. I pulled the plugs and the top one sparks about one half inch and the bottom one easy 9/16. One thing when I put the motor together I missed two 1/4 inch screws with gasket-like washers. Right after I put the engine together the lower cylinder worked very good. I took out the upper spark plug and the engine ran better, the upper plug was dry, the bottom one wet. Okay, fuel problem. Then I noticed fuel pouring onto the ground when the engine cranked over. Okay, bigger fuel problem. I took off the carburater cover and there it was, two holes that the 1/4 inch screws were missing. Fuel was poring out of these holes. I put the screws in. Everything back together and niether cylinder fired, even with both spark plugs pulled and sparking at 9/16 gap. I was thinking fuel problem because both cylinders are sparking properly, or powerpack because there were moments where the motor was running the rpms were going up and down without moving the throttle. The only thing I think fuel problem, when the screws were not in, the fuel from the upper intake leaked heavily to the lower intake supplying extra fuel. And when I fixed the leak the lower cylinder stoped working, as well as the top one. I would like very much to hear what you think of this one. Thanks much."
 
Back
Top