1974 Johnson 40 carb problem? Coils? Timing-have a few ?'s

Hello again,
Last summer some great ppl on this forum helped me revive an old motor and make her kick again and I'm hoping they can assist me again.

PROBLEM: Motor runs great at idle, under load at WOT it has a bad miss and can never reach top RPM. Last summer she would do upwards of 30, now she struggles to get to 20 and bogs hard.

ADDITIONAL INFO: As I said in my last post I have a carb for a 1967 johnson seahorse 40. Long story short a crooked boat mechanic in my area closed up and somehow "lost" my original carb. But motor ran great last season withthis carb.

THINGS ALREADY TRIED: Changed plugs, compression is great, decarbed the engine with sea foam, checked fuel hoses and primer ball.

Weird thing is that with the motor cover off she runs out A LOT better than with the cover is on I discovered this morning. Also I am wondering how to adjust timing on this or even if it is an issue. Also wondering about coils, both of mine have slight cracks on them I noticed today. Could this be an issue? How do I test them? Thanks in advance for any help u can offer.

Re: 1974 Johnson 40 carb problem? Coils? Timing-have a few ?'s

Cracked coils get moisture in them . when running they viabrate and eventually the ceramic will crack . you need an ohmeter to check resistance between wires . look for 2-3 ohms . i found mine 1st stop i made at a local marine shop . i found out here on the forum , these motors are vented through the cowl and are sensitive to air flow . ,....good luck w/ it