1997 Yamaha 25 HP carbs (MLHV3)

[littlebartlett]

I recently purchased a 14' jon w/ a 1997 25 hp Yamaha (MLHV3) w/o water testing. Hooked up to hose, started right up, ran fine. Took down to river, and bogs down when WOT, will run fine in gear at idle or with a little throttle. compression 150, 150, 140 (cold). Tested two gas tanks to no avial (thought tank was problem). Took apart carbs to find that they have been taken apart before. Found parts diagrams on www.yamaha-motor.com., but not enough detail. main jet #96 and slow air jet #54 numbers check out. I noticed two other jets when dissassembling carbs. They where on opposite side of main/slow air jets, opposite bowl/float side. Top jets where #140 & #120, Middle #140 & #120, bottom #140 & #150. Yamaha parts diagram (carb diagram # 15 & 16 calls these plugs, but are actually jets (underneath?). My question is this - should there be plugs in these holes or jets (I assume jets), and where are the proper locations for them (not enough detail on Yamaha drawing)? I would think that the top carb would have the bigger jets (#140 & #150, gravity?).

Would a repair manual from Yamaha tell me the locations of these jets? Are yahama manuals better than others?

Sorry so long, but need some help. I need to fish. I love it.

Bartlett

 

[Ray Neudecker]

Re: 1997 Yamaha 25 HP carbs (MLHV3)

They would be air jets and need to be carefully cleaned. Yamaha manuals are much better than the aftermarket in most cases. Don't expect much info on the carbs tho.

 

[nbrackin]

Re: 1997 Yamaha 25 HP carbs (MLHV3)

 

[nbrackin]

Re: 1997 Yamaha 25 HP carbs (MLHV3)

When cleaning carb,Did you run small wire(bread wrapper wire) through slow jets as well as all other? also may be gummed up in passage ways. may have to soak in carb. cleaner.Also be sure fuel filter is clean and no fuel lines are kinked

nbrackin

 

[littlebartlett]

Re: 1997 Yamaha 25 HP carbs (MLHV3)

They would be air jets and need to be carefully cleaned. Yamaha manuals are much better than the aftermarket in most cases. Don't expect much info on the carbs tho.

Any ideas on the right locations? The carbs were taken apart previously by someone else, and do not know if they were put back in right. They even added a socket head cap screw (originally a brass screw) over the slow air jet on 2 out of 3 carbs. I am going to soak overnight in carb cleaner, and clean with pipe cleaners.

 

[Ray Neudecker]

Re: 1997 Yamaha 25 HP carbs (MLHV3)

Most of the jets are sized for the hole and won't interchange. A thorough cleaning and reassembly should cure the problem. Those small carbs can be a real pain to get cleaned right.