1977 evinrude any ideas?

sorry, i have posted this already and did not receive any response. i have recently bought a 1977 evinrude 35hp outboard with a jet. i live in montana ele. 4500ft, motor came from missouri -500ft? plugs are showing way too rich with the low speed idle backed out 2.25 turns (dont want to fry it). yes, i will compression test this weekend. i understand it could be a jetting issue. what is a good jet size? i think i may have more of a problem. first some of the wire casings were melted when i recieved it. i can tell it has had a new headgasket done in the past from the paint missing, but not been completely torn into. i was TOLD it has a compression of 139psi in each cyl. what it sounds like is its not putting out the power for the rpm its giving, and its got a (double) miss at full throttle. bottom line its not getting my 14ft up to a plane. i also have a tach dwell meter that ill try to check rpms 5500-6000? does anyone have any exp. with this or know for sure? any ideas?

Re: 1977 evinrude any ideas?

The high speed jet is probably a 59D; try changing to a 53D. You won't get the same compression readings at higher altitude.

Re: 1977 evinrude any ideas?

thank you for your response, i have heard these motors have a common overheating problem is it true that it affects the head gasket before causing any other major damage. could this be the miss that i am hearing or could it be related to the high speed jetting? thanks again

Re: 1977 evinrude any ideas?

Some of the 1976 35HP motors had overheating problems especially in areas of heavy marine growth and were the subject of modifications in SB 1405. My understanding is that the 1977 models were modified at the factory.

If the engine is hot enough to blow the head gasket it is hot enough to do other damage including ignition component damage. The temperature inside the cowl can easily reach above 200 degrees. Be sure that your warning horn is functioning and add a temperature gauge if you want more insurance.