nitro outboard problems

[jhauschild]

hey.

I'm new at the the wonderful world of nitro boats and I'm startintg to hate it. I have a Cat. with a 3.5 outboard on it. Tha problem that I am haven' is that when I get it into the water and take off it seems to bog down and then sudenly take off, shooting out of the water several feet, and then it goes right back into the bog again, then doing it all over again and again. I have changed the trim and moved the motor up and down in the water with out much of a change. I also changed the richness lean and so forth, I got it to run a little longer that's it. Also the boat dies after a few jumps out of water as I explained earlier. I did notice that the fuel lines aren't very tight and there looks as if there may be some air in them. SO, what do I have left to do besides sell it and get a gas boat?

 

[ggillman]

Generally speaking, try this:

1) Use fresh fuel, nitro draws moisture big time, set your needle to the manufactures recommended setting for the run time of your engine, new,or broke in, and use a new glowplug.

2) Make sure the weighted end on the pickup tube in your fuel tank is not moving around and starving out.

3) Make sure your fuel tank vent is not covered up by fuel, should stick up in the little bubble on top of your tank.

4) Check your backpressure lines, from the lower unit on the motor to the vent connection.

5) Return your setup to the propshaft level with the bottom of the sponsons and parallel to the transom.

6) Check to make sure your throttle cable is not binding up from full left turn to full right turn on the outboard.

Follow the above steps and that should get ya goin,

Gene ;D

 

[Ron Olson]

Don't feel like the Lone Ranger, we've all gone through the learning curve. Check your fuel lines or replace them with medium sized ones. Use zip ties if needed to hold them in place. The motor may be running lean. Try it about 3 turns out and go from there. Check the brass tubing for cracks or kinks. There are a lot of good outboard boaters in here so hang in there! I wonder how I did it without the Internet.

 

[MikeP]

jhauschild,

Explaine a little more detail on your Bog, Sounds more like cavatation when it shoots out of the water for several feet then cavatates again. From a bog it usually takes longer to get going. Tells us about your motor, props, fuel.

Mike

 

[chunk t]

I had suffered through a very similar problem the first time I put my first o/b boat on the water. It was a KB3.5 from '84 w/ the black carb. it was as iff it was vasilating from too lean to too rich. The hull would do an awsome water wheelie for 3 feet than burble (too rich) and cavitate the prop for a moment and go lean again and jump out of the water. And the cycle would continue.

Ended up the threads for the fuel barb on the carb were stripped from the factory. A small amount of air would occasionally sneek in leaning out the engin. I bought a new carb and the problem went a way.

When the engine is running carefully watch the fuel flow through the fuel line. When the engine kicks over and runs on it's own the fuel should flow fairly quickly.

ct.

 

[chunk t]

sorry about the repetetive posts guys. I kept getting router errors.

ct

No problem, let Tom know if it keeps it up, he just

updated the forum, I deleted the extra's,

Gene ;D

 

[Ron Olson]

That's one way to become a Top 10 poster! seriously though, some other things to look at especially on an older motor is the fuel nipple on the carb. some of them went too far in choking off the fuel. also make sure that the nut that holds the needle valve in place is snug to keep the needle from moving around.

 

[MHowarth]

You may want to check out your center of gravity, and richen the heck out of it. The boat shouls run no matter how it's set up. But if the motors lean, it will quit. It may hop and go all over, richen it out and work with the setup of the boat later!

 

[Jerry Dunlap]

Maybe I missed it in the previous posts, but the propeller selection can make a big difference. I think the most user friendly 3.5 outboard propeller is the Octura X440. It would be helpful to know the type of hull, i.e., Dumas Hot Shot Sprint(I could really help out on that one), Prather Lap Cat, Bandit, whatever.

Jerry Dunlap

 

[TimD]

jhauschild,

Do you have the fuel tank pressurised? There should be 2 lines coming from your tank - 1 goes to the carb and the other to a pressure fitting on the exhaust.

Other than that, Does the glow plug element look shiney?