Engine drops rpm's

[spicerak]

1987 evinrude 150... The engine idles perfect dosent stall... Trying to get in plane is doggish but it does kick in a few minutes and goes.... As it running at 4800 rpms its will just drop down rpms and sonetimes goes up... Sonetimes it will run perfect at 5200 rpms will no dropping rpms... But it seems like power issue... Compression is perfect.. Any suggestions

 

[boobie]

Re: Engine drops rpm's

Do a cyl drop test on it to see which cyl is not firing. Could be carb or ignition prob.

 

[emdsapmgr]

Re: Engine drops rpm's

After you finish boobie's tests, there is a fuel test you can do. When the engine starts to lose rpm's try constantly priming the fuel hose bulb. That will force extra fuel into the carbs. If the engine runs fine when you constantly prime the fuel hose bulb, you have a fuel delivery problem-possibly a weak fuel pump.