Well I got a new OS .18 engine for my BJ26 about a yera ago but havent ran it much. I've only ran about 3 tanks of fuel through so far. Why? Because it bogs at WOT for some reason. I have checked it for leakes, checked the drive wire to make shure its not slipping, but still past 1/2 throttle it bogs and dies after it revs high only for a few seconds while puffing a nice cloud of blue smoke. I have leaned it out 2 hours from the factory setting, still getting plenty of smoke and a little raw fuel out the back....any sugestions?

These are old pictures of my rebuild.


I think I'm just going to throw the ported .15 back in there. At least with that engine I could run it at WOT all day with out an issue.

How many turns out is the HSN??

How long is the pipe, from center of engine, down the header, to largest part of the pipe??

What pipe is it?

Have you checked your fuel system for leaks??

Does the header match up to the exhaust port (looks like there is a spacer in there or something)?

What prop are you using?

Sean

In addition to Sean's questions, also let us know the prop, plug, and fuel you're using.

Frankly, from the description, it sounds lean. You can't base your settings off the way it came from the factory. Count the turns while you screw it closed and report back.

Thanks for the quick replys.

Prop-Grim Racer 42x55
Pipe-Proboat, the one that came with the .15
The fuel system has no leaks. I have tested it with a hand pump and everything is good.
The pipe flange matches, the "space" is a black gasket.

I need to check the high speed needle turns and the lenght of the pipe.

Sean and Chuck,
correct me if I'm wrong but isn't the Aqub 42x55 prop a bit big for the .18?

The reason I ask is according to the chart on Aqub the 42x55 is equivalent to a Prather 230 and a 230 is what we use with the K&B 7.5cc (.45) on the Tunnels.

and I tend to agree with chuck also, it sounds lean. let us know how many turns out you have on the HSN.

Dan.

Yup, the prop sounds too big. A prop that's too big can overload the engine and cause it to overheat. A .21 would use a Prather 220 or 225. A .18 should definitely step down a notch. I haven't run this boat, so I can only estimate that something like a Prather 215 would be a good starting point. Perhaps the Grim 40x53?

Thanks for the heads up on the prop. I bought that one because I read in the SV thread that that's what every one was using with the stock 18 as an upgrade in the SV. I figured that the OS .18, rated at over 1.5 HP being .5 more than the AQ motor, would turn it with no issues....toal n00b assumption[:@]

I have a pair of plastic Miss Bud props. I'll throw one of those on there and see if that fixes teh problem.

Thanks again guys!

losi,

I just went and search the SV27 thread and beside the Octura X series the best Grim prop that are recommended for the SV27 Nitro are the 40x53 and the 40x52/3 prop.

the 42x55 would be better suited for the Brushless SV.

Dan.

I'd wait until you can get a metal prop of the appropriate size.

Good eye Dan...I just took for granted it was the prop they recommended for the MV...

Just got back from the Dallas boat race...so did not have an opportunity to watch this thread.

Sean

Bring the LE out flush with carb. body. Then screw in 1/2 turn. Top end 2 1/2 to 2 3/4 turns out. Prop is to big. Go to a Y536 prop. You may not be getting enough vac. to the gas tank the way it is set up. Run a vac. line [almost] to the fat part of the tune pipe. That motor should scream

You could also try a 3.5 tune pipe on it. I'd used a MAC 3.5 in my Miss Bud with a vegas.18 and she got on the pipes just great!!! ran alot faster then the stock2.5 tune pipe.