200hp 81 evenrude power loss after warm up

[timaud]

Hello all;<br />We have an 81 Evenrude that starts good cold and idles good also for warm up, goes in gear fine and idles in gear fine out past the no wake buoy's (1/4 mile) but once in open waters and we go to gun it or just break plane it dies. When we choke it as we give throttle it slowly taakes off and then like a bat out of he**. All fuel lines are new and carb's newly rebuilt with floats and gaskets. We are using newer Spark plugs (??what a local Mechanic told us??)high octane fuel @ 50:1 mix and an octane booster. But here's the kicker when ffinally running @ high idle, it runs real good @5700rpm and all of a sudden stalls out (almost like the engine siezed) and will not turn over for a few minutes. <br /><br />There is alot more info I could give if I new what was needed to help us diagnose our problem. Thank you to all in advance for any and all help you could give us.<br /><br /> timaud@lvcm.com <br />Tim & Audrey<br />[*]null

 

[NathanY]

Re: 200hp 81 evenrude power loss after warm up

I had an old 115 Johnson that did that, come to find out that it was the the coil pack. Would run real good till it got hot.

 

[clanton]

Re: 200hp 81 evenrude power loss after warm up

What kind and number of newer sparkplug.

 

[ICEMAN]

Re: 200hp 81 evenrude power loss after warm up

Hi, Have you done a compression test? I would do that, If you motor is seizing, it sounds like you may have a bad cylinder. Remove the spark plugs and look at the electrode. If one looks quite different from the others, that cylinder may have a problem.

 

[timaud]

Re: 200hp 81 evenrude power loss after warm up

The new Plugs are NGK B7HS - 10, And yes I did a compression test and all were the same psi, We took the boat out again today and found that if we keep on choking it it runs pretty well but still not to full potential, we were getting about 4500 rpm out of it and when we first got it we were able to get 5800rpm.<br /><br />Now, the motor in question is from the Pacific ocean and now it is being used in Lake Mead about 2800 Ft. above sea level, might this have anything to do with it, maybe the jets?<br /><br />No, we do not want to keep choking it as I believe it will burn out the electric choke.<br /><br />If we choke it to gett it into plane and then release the choke it seams to run pretty well for a little while and then it sounds like it is starving for fuel and that is when it might seize up or just choke it again and all is somewhat fine again.<br /><br />Again thanks for all your help in advance<br /><br /> timaud@lvcm.com