33 HP Ski Twin runs rough at wide open throttle

flyerdustin

Recruit
Joined
Aug 7, 2013
Messages
1
My first post on this forum so let see what kind of responces i can get.
Ive got a 1969 Evinrude 33 hp Ski Twin model 33952A that is mounted on a new to me 1961 16" Lyman runabout. the boat and engine had sat since 1997 so i was warry about how the ski twin would run. I ran it in a trash can and she started but didnt want to run very smoothly or idle without lots of choke. We all know what that means, carb rebuild time. Pulled the carb off, disassembled, soaked, blew out and reassembled using a new carb kit with new float. Set carb float to level with bowl. Reassebled and installed back on engine. Test ran and adjusted low and high speed needles. Ran well on 1st sea trial if not a perhaps a bit sluggish but just about what i was suspecting for the age and size boat it is mounted on. secound sea trial about 20 min into trip it began to run rough just at wide open throttle. made it to destination and shut down for about 2 hours. normal start up and idle out as soon as i go to wide open i get the same roughness. Tried adjusting high speed needle with no luck other than being able to make it completly die by making way to rich or way to lean. Any ideas? Im thinking i need to look into the points/condensor/coil or i maybe a weak impeller causing her to overheat? Please correct me if im wrong but ive looked all over this engine and cant find a cooling water **** whole. The water exits though the exhaust and the small hole at the trailing edge of the tower.
Thanks
-Dustin
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 33 HP Ski Twin runs rough at wide open throttle

Welcome to the forum.
Your engine does not have a tell-tale, water will come out of the exhaust port.
It sounds like you may have a coil breaking down at high RPM, use an inductive timing light to watch the spark on each cylinder at high speed. Have you removed the flywheel and checked the points for proper gap and to see if there are any cracks in the coils?
 

kfa4303

Banned
Joined
Sep 17, 2010
Messages
6,094
Re: 33 HP Ski Twin runs rough at wide open throttle

HI Dustin. Welcome to iboats. I used to have a '66 33hp myself. I agree with Daviet, and suspect you may be dropping a cylinder at high speeds. Here are some handy articles that can walk you through an entire tune up from top to bottom. You can get any routine parts you need for the job right here at iboats.

Reviving a Vintage Big Twin - Part 1
5.5 HP Evinrude Johnson 1954-1954 Carburetor Tune-Up Procedure (great carb rebuild link)
3 HP Evinrude Lightwin Ignition System Tune-Up 1952-1967 (great ignition rebuild link)
1969 Evinrude 33952A 33 hp Outboard Motor Parts (Parts catalog)
 
Top