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upper engine mount questions -- 1974 Evinrude 25hp

chaos421

chaos421

New member
Hey guys,

1974 Evinrude 25hp 25402M

I'd like to know if anyone has had my same problem. I've been working on this old Evinrude for the past year off and on. The initial problem has been that it idles poorly at low speeds. I've replaced most of the electrical system including points, ignition coils, condensers, etc. I verified the timing. I checked and replaced the reed valve that was bent. Of course the carb was cleaned like 5 times. It actually was running pretty well in the barrel, but when I got out to the lake it would cough and sputter if I hit some waves. I think my current (?last) problem might be rotten upper engine mounts. Leeroy's says (http://leeroysramblings.com/Johnson_9.9_powerhead.htm) I should remove the whole powerhead, but his examples are a bit different from mine. I believe that with lots of vibration, it is shaking the crankshaft relative to the armature plate causing the timing to be off a split second. The replacement part seems pretty expensive so I was also wondering if anyone had replaced this with a solid bolt, or with some similar automotive mounting bracket.

See Part #8
http://www.marineengine.com/parts/j...manufacturer=Evinrude&section=Exhaust+Housing

Thanks,
Keith


IMG_9756.jpgIMG_9757.jpg
 
So , is the mount broken ?---------The 9.9 is a totally different mounting set up and not relative to what you have.------------What is the compression on this motor.-------------What is the side to side play on the armature plate ?--------Have you had the armature plate off to inspect the bushing on it?-------Should have been off when you did the coils !
 
racerone said:
So , is the mount broken ?---------The 9.9 is a totally different mounting set up and not relative to what you have.------------What is the compression on this motor.-------------What is the side to side play on the armature plate ?--------Have you had the armature plate off to inspect the bushing on it?-------Should have been off when you did the coils !
Click to expand...

No, the mount isn't broken, but the rubber seems really sloppy because there is a lot of side to side play.
Yeah, the 9.9 seemed totally different.
I remember checking compression last summer with a friend who is a mechanic and it was normal, not sure what the number was.
The armature plate is fixed. To set the points I used a special tool (http://www.franksoutboardtools.com).
I did not remove the armature plate.
Sounds like I may have to remove it all to get down to the mounts.

So does my explanation about how I think the side to side motion is throwing off the timing? I'd hate to take it all apart down to the mounts and rebuild it all to have the same dang thing.

Thanks,
Keith
 
I dont believe you need to take it all apart the upper and lower front mounts might be difficult. There are six mounts total and most are fairly cheap used on ebay. The motor will shake if not running properly and too your other question do not hard mount t you will rattle the rivets loose on the transom. How did you set the points? You can check the timing with a light and a car battery. There is a single mark on the flywheel and on the outer edge of the points plate are two sets of marks 180 degrees out.
The flywheel mark needs to be in between the two marks. Ignition timing is on points gap start out setting the points at exactly .022 for that type of ignition. It will run alot smoother and the carb will also adjust better. When adjusting the slow needle do it slowly 1/8 turn at a time and wait for the engine to respond. Turn it in until the engine stumbles and back out slow until you get a smooth idle and add 1/4 turn. If the needle is easy to turn snug up on the packing nut.
 
racerone said:
I do not believe the issue is with the motor mounts !-----So more trouble shooting.
Click to expand...

Thanks racerone, I was talking with a friend and he thought it was more likely the cylinder ports would be narrowed. What was happening last fall was that the motor was working fine in the bucket, but would bog down when it hit waves. He said, well if it is bogging down under load perhaps the ports on the cylinder (in or out) may be plugged with carbon deposits. He suggested going in there and inspecting them, and that they may need chiseling out as they can get very hard.

Thanks guys!

Keith
 
chaos421 said:
Thanks racerone, I was talking with a friend and he thought it was more likely the cylinder ports would be narrowed. What was happening last fall was that the motor was working fine in the bucket, but would bog down when it hit waves. He said, well if it is bogging down under load perhaps the ports on the cylinder (in or out) may be plugged with carbon deposits. He suggested going in there and inspecting them, and that they may need chiseling out as they can get very hard.

Thanks guys!

Keith
Click to expand...
No that is a bad idea I have never seen a 2 strk ports fill up with carbon much less need chiseling. If you want to clean your motor use BRP ENGINETUNE OR MERCURY POWERTUNE to clean the carbon out. How big is the boat the motor is on and what is compression needs to be checked. Did you do the link and sync
 
I believe you need to do some organized trouble shooting, instead of a lot of guessing.----------What are the compression numbers ?---------Does spark jump a gap of 3/8" on both leads ?---------Is throttle opening at the correct time ?-----Have you checked for a ruptured diaphragm in the fuel pump.---Have you checked the fuel tank internals ?---Is the thermostat installed and working properly ?----Was the high speed jet removed from the bottom of the carburetor bowl ??
 
Thanks for the help guys.

Yeah I agree more testing makes sense. I think I'll put everything back together and do some trial runs, and testing and get back to you guys.

Compression: I'll have to test it again.
Spark was strong, I'll have to test if it jumps that far
Throttle opens correctly
Fuel pump is new
I've replaced fuel tank gasket but didn't do much else there.
I'll have to look at the thermostat
High speed jet was removed and cleaned, but replaced.

Thanks again,
Keith
 
chaos421 said:
Hey guys,

1974 Evinrude 25hp 25402M

I'd like to know if anyone has had my same problem. I've been working on this old Evinrude for the past year off and on. The initial problem has been that it idles poorly at low speeds. I've replaced most of the electrical system including points, ignition coils, condensers, etc. I verified the timing. I checked and replaced the reed valve that was bent. Of course the carb was cleaned like 5 times. It actually was running pretty well in the barrel, but when I got out to the lake it would cough and sputter if I hit some waves. I think my current (?last) problem might be rotten upper engine mounts. Leeroy's says (http://leeroysramblings.com/Johnson_9.9_powerhead.htm) I should remove the whole powerhead, but his examples are a bit different from mine. I believe that with lots of vibration, it is shaking the crankshaft relative to the armature plate causing the timing to be off a split second. The replacement part seems pretty expensive so I was also wondering if anyone had replaced this with a solid bolt, or with some similar automotive mounting bracket.

See Part #8
http://www.marineengine.com/parts/j...manufacturer=Evinrude&section=Exhaust+Housing

Thanks,
Keith


View attachment 12981View attachment 12982
Click to expand...

I want to let people who read this in the future that you do not have to remove the powerhead to replace the upper rubber mounts!!!

This can be done by tilting the motor all the way up and using a small wrench.

If you have to, bend a wrench with a little over a 45 degree angle. Use some heat and in a bench vice, bend a short wrench. The one I used was about 4" long. All you have to do is get the rear bolt loose enough to slide the mount out and the new one in.

Hope this helps someone out in the future. And if your motor is rocking left to right check the rubber mounts, there is a good chance they need to be replaced because they do wear out! It's not automatically a rough idle. It could be running perfect and with bad worn old mounts, it will rattle your entire boat!!!

Bless the man or woman trying to get their boat on the water!
 
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So post # 2 says that the mounts are totally different than a 9.9 model.-----Now that your mounts have been replaced how is the motor running ?
 
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