1969 Evinrude 25hp Sportster issues

[Whittle]

I rebuilt this motor with the help of my nephew about 7 years ago. It was given to us by a guy who couldn't get it running. I've got it mounted to a 16?48 Lowe Big Jon. The problem I'm having is that we can't get it to plane with the two of us in it. Canged the seals, water pump, points and condensers. I recently found out that the siphon in the tank was loose. Tightend that up and getting ready to replace the fuel pump. And suggestions on what else I can look into would be greatly appreciated.

 

[hardwater fisherman]

Check for good spark on both cylinders.

 

[Whittle]

I've got good spark on both and compression check shows 120 even on both cylinders.

 

[AlTn]

did it ever plane this boat with both of you in it?...do a cylinder drop test while out on the lake < remove one plug wire at a time and the drop in rpm should be equal on each cylinder..if the motor won't run with one wire off then that cylinder is the one doing all the work...if both cylinders respond the same in rpm drop then it's time to move on to another cause >...may be as simple as pulling the spark plug boot off the wire, cutting 1/2" off the wire and reattaching the terminal end and boot...post back when you know more

 

[bspeth]

it trimmed out right,does it have a high speed adjust?

 

[Whittle]

I'm thinking of getting a Tiny Tach to check RPMs at WOT. May be changing the prop. Right now it has a 10" pitch. I adjusted the points and replaced the fuel pump. Sounds like it revs a lot higher in the test tank. Also not sure if the motor is mounted at the right height. The cavitation plate set's about an inch or two below the bottom of my flat bottom boat. I noticed that the water intake on this motor is right above the cavitation plate. I'll definitely let you guy's know more when I can properly check the RPMs. Until then please let me know what you thing about the mounting height.

 

[Whittle]

Also I trimmed out the motor at one hole from the top. This motor has a non adjustable high speed jet so there's nothing I can do there.

 

[hardwater fisherman]

I learned here the main water intake is below the plate in the piece sticking down above the prop.The intake you speak of is for when you are in reverse.If you are 2inchs below the bottom of the boat that might be too low.

 

[AlTn]

on plane...is there just a "film" of water running over the cavitation plate?..as hardwater states, the main water intake is a passage covered by a screen which is just separated from the underwater exhaust "snout"...you'll see it just below the av plate

 

[Whittle]

No "film". It looks to be under the surface. I'll raise the motor so that the plate is even with the bottom of the boat and see if that helps. I'm glad to hear that the intake is were you guy's say it is. That makes a lot more sense. I also heard that the spark plugs (Champion J4C) should be gapped at .030. Is that correct? The motor is model 25902B.

 

[LK_Shastina]

My 1969 25hp Evinrude suddenly stopped planing my boat. It seemed to run and rev ok. The problem: The prop was slipping. The brass insert became loose and was spinning inside the mounting hole.

 

[southkogs]

This topic is a few years old. Let's let it rest.