1975 evinrude 70hp wot bog, surge

Just got back from 3 days on the river, had an issue- motor gets right out of the hole and on plane good and will run at 4500-5000rpm all day (runs really good) but if i try to punch it for wot it approaches 5500rpm and then looses power(feels like i let off the throttle) and then itll start surging up and down (rpms)untill i back off throttle to 4500 rpm which it then will run all day. Just rebuilt fuel pump before trip couse i thought that was the prob. I do have one of those glass in line fuel filters, should i get rid of it? Does this on both fuel tanks.
Engine is 1975 70hp, boat is a 1965 16` starcraft (in my pic) timing is correct according to joe reeves method and compression is good.
Thanks in advance for any help, xj

Re: 1975 evinrude 70hp wot bog, surge

You might want to check the high speed orifices to see if you have one restricted or plugged.
Try pumping the primer bulb when it bogs down and see if it helps.

Re: 1975 evinrude 70hp wot bog, surge

Daviet said:

You might want to check the high speed orifices to see if you have one restricted or plugged.
Try pumping the primer bulb when it bogs down and see if it helps.

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Dam, forgot all about pumping primer when this happens. The high speed jets are behind the drain plugs right? Thanks for the reply, unfortunately its gona be a little while before she gets back on the water, need to buy new($$$) lounge seats or rebuild mine, the darn backrest broke on it and i found all the wood to be completely rotted.