Lost speed/power at altitude.


Old 08-10-00, 09:19 PM
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We moved from sea level to 4900 ft above and now our 1988 Four Winns 21.5 cuddy has lost speed and power. Have OMC V-8 220hp 5.2L; used to get easily 5000 rpm and 45+ speed. Now barely get 3800 rpm and tops out at 25 mph. Have jetted down the carburetor, changed the prop pitch from 19 to 15, and adjusted the timing several times.
Any other suggestions?
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Old 08-13-00, 09:41 AM
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The only difference from you previous location is oxygen. Rejettting the carb leaner as you have done is the best way to get the engine to perform as desired. In some cases
a drop in prop pitch is necessary and you have taken that as far as i would recommend.
I would reset the timing to its original spec, and for that model shoul be 8.btdc.
be sure to ck the dwell and the advance mech in the distributor. if it performed fine just prior to the elevation change.. then i would say you need to change the gear reduction in the outdrive.
Its is going to be necessary to get the rpms up higher (low pitch prop) to get you the power you expect. Dont however expect it to be as fast as it was at sea level.
Old 08-14-00, 08:37 PM
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Thanks, I'll try it. Would checking the compression be of any use?
I don't expect the same speed, but some speed would be nice, it just seems that much loss of performance is unreal. Especially with everyone with an outboard passing me by.
Old 08-27-00, 06:11 PM
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A compression check and tune up by a mechanic at the altitude would be recommended. but if it was running fine the time before then its not neccesary Scott

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