1972 Evinrude 25hp power loss

[kfc1188]

I recently purchased a 14' fiberglass boat with a 25hp Evinrude outboard. I am having some problems with power loss at full throttle. Sometimes the engine works perfectly, but other times it only runs at 25% speed. It usually runs this way for a while and sometimes gags and goes to full speed. Does anyone have any suggestions for me? I just replaced the spark plugs, but the problem persisted. I am starting to think that there may be a problem with the carburetor. How can I obtain a breakdown print of the carburetor so I can clean it? Thanks in advance for any help.

[Boatist]

KfcWelcome to the board. First thing you should do is get a manual it will save you TIME, PARTS, and MONEY over time. Look on bottom of page for manual.I would make sure have good spark on both plugs, should jump at least 3/8 of a inch. If no spark from one cylinder or weak then time to pull flywheel and check or replace points and condenser for each cylinder. When it is running bad try pulling plug wire off one at a time to see which cylinder it is. Check compression on both cylinders, Shold be even and 100psi. If low or uneven then decarb the engine and see if that helps.When running bad pump the primer ball and see if makes any difference, also pull the choke our a little or for a short time and note difference.By this time should have a idea where problems lies. Follow the trouble shooting in your new manual.

[JB]

Before you buy a manual, KFC, you need to identify the model number and get the correct year of your engine.Good luck.

[kfc1188]

I checked the fuel ball and it is full when the motor is malfunctioning. Also, i have tried pulling the choke and it just bogs the engine down. I have even tried adjusting the idle mixture screw (lean to rich) and it doesn't seem to help. Possible clogged jet or stuck float?

[Boatist]

KfcNeed to check spark and compression and then should have good idea where to start. With what you reported about fuel pressure and choke I dout it is a fuel problem. My wild *** guess is no spark on one cylinder. Your are not going to know until you check spark and compression.