1984 Evinrude 35hp loss of power and rpm at wot (Video included)

[RRaulH]

I've been trying to find an explanation for my sudden loss of power and consequently a lower rpm at wot. I've been reading a lot of post on here and other forums, but have yet to find a solution or explanation for my problem. I hope some of you might be able to shed some light on my situation. I have a 1984 evinrude 35hp outboard engine mounted on a bracket with a setback of +/- 1 ft this is mounted on a 16 ft cranchi motorboat. I've had this motor for about half a year now and have had no major troubles with it, besides my loss of power in the last 2 weeks. I'm running clean fuel, new spark plugs and have disconnected the choke from the carb which seems faulty since it keeps pumping fuel whether on or off . The motor still starts up on the first try every single time, and seems to run good.

The motor seems to have lost some power and rpm. Before I was getting on plane quite easily with 2 people on board, which now is just doable but topspeed has drastically reduced. I used to be able to get a top speed of around 25mph at wot and now this had dropped to around 20mph with only the driver on board. With an additional person on board the speed is greatly reduced from +/- 23 mph to around 15 mph at wot. I've added a video of the engine running at wot before and after so you can hear and see the difference. Any help would be greatly appreciated.

Additional info:
Boat 16 ft Cranchi
weight 1100 pounds with driver
Outboard 1984 evinrude 35 hp 20"longshaft on 1ft setback

Video: before and after

 

[fireman57]

When is the last time you went through the carbs? You could have some crud in one of the high speed jets that is restricting the fuel when it needs it. make sure you run a small piece of wire through them and blow them out good with carb cleaner.

 

[RRaulH]

Thanks for the reply. I have actually done nothing to the carb so far. Are there multiple high speed jets? I have a single carb set up. How easily is this done? Do I have to take the carb off, or can it stay on the engine?
Just wondering, does the low speed needle (idle needle) have any influence on the engine at higher rpm?

 

[AlTn]

one "high speed jet" < office plug >..no influence to ? about idle mixture needle vs. higher rpm..the office plug is behind either a screw or the fuel inlet nipple on the bottom of the front face of the carb bowl...remove either the nipple or screw and you can try to clean the office plug in place, it'll be about in the center of the fuel bowl directly behind either fitting...you may have success with carb cleaner w/ straw attachment directly inserted into the jet, followed up with a shot of compressed air to clear it out, may try this 3 or 4 times, buckle things back up and give it a try on open water. It's all a matter of clearance as to whether you can do this in place or have to take the carb off and give it a full cleaning.

 

[RRaulH]

you may have success with carb cleaner w/ straw attachment directly inserted into the jet, followed up with a shot of compressed air to clear it out, may try this 3 or 4 times, buckle things back up and give it a try on open water. It's all a matter of clearance as to whether you can do this in place or have to take the carb off and give it a full cleaning.

Ok thanks, will definitely try this.

one "high speed jet" < office plug >..no influence to ? about idle mixture needle vs. higher rpm..

Not entirely sure what you mean. Let me try to clarify. Does the Idle adjusment needle or (Single S/S Adjustable Needle Valve) as it's called in the carb cleaning tuturial on this forum, have any impact on the way the engine's running at higher rpm?
Or does it have no impact whatsoever when rpm increases above idle rpm? The reason I'm asking this is because the engine seemed to run somewhat smoother after adjusting the slow speed adjustable needle valve.

 

[RRaulH]

Well, the carb cleaning seems to have done the trick, so thanks for the help!