Help!- engine surging under load 91 25hp

[tls4136]

Hello-

I have a '91 model e25teeie and it runs completely fine on ears no problem. when i get under load it wont go above 1/2 throttle without bogging. at full throttle it maybe goes 1/2 speed. The weird part is if i remove the cowl and "hand choke" the carb it will run full speed no problem, until i remove my hand and then back to normal. it has enough vaccum that it wants to pull my hand over it when i do this. Here is what i have had done to it.

1- rebuilt carb 2x
2- new diaphram fuel pump
3 replaced fuel lines int/external
4 new fuel tank/ primer bulb
5 new gas connection
6 new spark- has 120 comp each cyl

it sounds like the air fuel ratio is off, i have no idea how to adjust it or if it is adjustable.

Should it have some type of air filter?

there is an adjuster on the throttle linkage. I have not idea what it is.

i have been trying to get this running since October last year.2 different mechanics. Please help

I don't know how to edit the pics if they are too large. I'm sorry. thanks for your help.

[ez__rider]

that pic of your carb... you see the phillips screw at 12 o'clock: it is the fuel mixture screw. I don't necessarily think F/A ratio is your issue.

I don't have an air filter either, was told they aren't necessary.

I'm having an occ***ional bogging issue, so I'll be curious what other responses come in. It does sound like a fuel delivery problem to me.

[Elton Smith]

I have that exact engine on my boat and it was doing the same thing.What was going on was it was vibrating every thing loose,including the engine mount bolts.Check everything including the carb bowl and see if anything has loosened up.I safty wired every thing I could Then tie wrapped the carb.As far as the air filter they never had one.They used to use an air silencer so you couldn't hear the carb.