Help with 1990 Yamaha 115 cutting out during take off but fine on top end

[ZX10R]

My dad is on vacation with our bass boat and ran into a problem and has called for help. I am not with the boat but this is what he says it is doing.

The engine starts fine, idles fine, and runs great on top end, but when he powers up to take off it starts cutting in and out. He has to flip the switch for the choke in order to get the motor to pick back up. Once he gets passed take off and is on top end running the motor is fine and runs great. It is only during take off the engine cuts in and out.

Thanks for only help

2-Stroke engine

 

[Bamaman1]

Re: Help with 1990 Yamaha 115 cutting out during take off but fine on top end

Take it in steps.
Change the spark plugs is #1. Any Autozone or Advance Auto Parts sells the plugs cheap.
Step #2 would be to check out the fuel line. 90/10 gas is terrible on anything rubber. Also check the siphon in the fuel tank to make sure there are no obstructions. Also make sure the fuel bulb is good.
Step #3 is to change the fuel filter under the carbs.
Step #4 would be to change the rubber membrane in the fuel pump--also under the carbs by the fuel filter.
Step #5 would be to remove the carbs, disassemble them and clean them with aerosol carb cleaner. Reassemble and reinstall on the engine.

The cost of doing these maintenance repairs is maybe $60, and it's something it doesn't take a mechanic to do. Cleaning the carbs doesn't even take a carb kit if you're careful with the gaskets.

He should then be up and running fine.

 

[ZX10R]

Re: Help with 1990 Yamaha 115 cutting out during take off but fine on top end

Thanks for the response

I know we just replaced the entire fuel line this past month and replaced the fuel pump membrane at this time also. But the other things we need to check as you said.

 

[Toddboat]

Re: Help with 1990 Yamaha 115 cutting out during take off but fine on top end

I'm no marine mechanic, but I have a similar problem with my boat which I've learned a lot about since I've been trying to fix it. I've learned that there are 3 circuits in the carbs... one for idle speed, one for low (intermediate) speed, and one for high speed. It's possible for one circuit to get clogged and not the others, making the boat run poorly only at certain speeds and not at others. It's possible that your intermediate jets are clogged in your carbs. One thing I've learned is that spraying them with carb cleaner is not enough. You need to soak them for two days in something like Techron, completely submerging them after removing all of their rubber and plastic parts. Once you take them out of the bath, then you spray carb cleaner through all jets and other orifices. The gunk that clogs them could be the fuel that was left in the carb bowls over winter storage if you didn't properly treat the fuel with stabilizer before storage. Just my 2 cents because I've been dealing with the same issues.

 

[ZX10R]

Re: Help with 1990 Yamaha 115 cutting out during take off but fine on top end

Thanks Toddboat,

The boat ran fine last year but the two times my dad has had it out this year same problem. Runs great at idle and top end but low speed it just cuts out.

 

[Toddboat]

Re: Help with 1990 Yamaha 115 cutting out during take off but fine on top end

You can rule out fuel pump issues by being your own fuel pump. When it bogs down, try priming the bulb to see if it picks up. I doubt the fuel pump is the issue because if it were, it would likely run poorly at all speeds. I still think it's the intermediate jet in your carb/s. In mine, there is a small pinhole that connects the high speed jet to the intermediate speed jet. It's through this pinhole that the intermediate speed jet gets its fuel. There is a way to spray carb cleaner through it, but you first have to hold your finger over the end of the high speed jet to force the carb cleaner to go through the intermediate jet. I think this is why they recommend a bath in carb cleaner, because most people don't know where the holes are, or how to effectively clean them. The bath in carb cleaner is more idiot proof than just spraying through the holes you do see.