Nova 45 DD going lean?

[Tim Kish]

I have a sneaky suspicion that there is either to much clearence in the engine to crank or pto. Or there is just not enough fuel (oil) inside the case to keep it sealed properly after it warms up and cleans out..

I am going to tear down my friends engine after this coming weekend and start measuring everything.

Will post what I find.

 

[Andy Brown]

Stock Nova carb + .350" stinger bore + fully enclosed sport hydro = engine that blubbers on the beach and leans out on the water.

Add Mid Simmer heat to that issue and the problem gets worse.

 

[Terry Keeley]

Stock Nova carb + .350" stinger bore + fully enclosed sport hydro = engine that blubbers on the beach and leans out on the water.

Add Mid Simmer heat to that issue and the problem gets worse.

Thanks for the input, we ran Olly's without the cowl and it came back cool, same issue. Tim ran 3 different pipes on the other motor.

Not bashing as it's very strong when it goes and they all have their quirks, but we have some very experienced folks scratching their heads with this.

In the other case (NLMBC member Al Long that Tim is helping) he had a good running JAE with an AA45, he switched only the motor to a DD and is having the same issue Olly and others are.

The motor just has a hard time drawing fuel.

And, don't worry, we'll find it!

 

[Olly]

I can't find any cracks in the motor. Do those of you with Frank Orlic carbs have this problem? I am trying to narrow it down to a motor or fuel problem.

Thanks

Olly

 

[Mike Betke]

Olly,

On the wrap around motor that we run, we have not had any issues with the stock carb drawing fuel. Our carb has the low end needle cut out of it as well and we run standard medium size dubro fuel line. Check the seal bores between the bearings. Does the exposed bearing on the rotor have a seal on it?

Andy might be on to something as well. I had this problem on my scale a while back where it would quit running after 5 or 6 laps. I ended up fixing the fuel draw problem by reducing the stinger size on the pipe.

 

[RonShaw]

I can't find any cracks in the motor. Do those of you with Frank Orlic carbs have this problem? I am trying to narrow it down to a motor or fuel problem.

Thanks

Olly

Olly,

If you have checked the bearings and they are ok, put the stock carb back on the motor and run it to see if it is ok. If it is, you have found the culprit and can start looking at why such as the bore being too large, etc. The NR 46 is a great engine so I am sure you will figure it out soon.

 

[Andy Brown]

Olly,

On the wrap around motor that we run, we have not had any issues with the stock carb drawing fuel. Our carb has the low end needle cut out of it as well and we run standard medium size dubro fuel line. Check the seal bores between the bearings. Does the exposed bearing on the rotor have a seal on it?

Andy might be on to something as well. I had this problem on my scale a while back where it would quit running after 5 or 6 laps. I ended up fixing the fuel draw problem by reducing the stinger size on the pipe.

Ok, if the DD engine is having the problem and the wrap around engine did not, then the other problem could be the PTO seal. Some of you guys know that Rod G. was adamant about the importance of the PTO seal on OB engines. Maybe Nova did not pay close attention to that detail.

Even so, a bigger spraybar bore, (about .100") for better fuel delivery and a bigger stinger diameter (about .420") to let the heat out would cure the problem, even with a poor PTO seal. That combination will let the engine idle cleanly on the beach with less than half throttle and the engine will get the fuel it needs under a load.

 

[Jeff Schindler]

I usually leave it up to the pipe designer to know more about the pipe parameters than I do, especially if its the same brand as the engine.

Having said this, If I want to experiment with reducing the stinger on a NR46 muffled pipe, what would be the best way to do this? I have an idea of how to do it, but I'd like to hear some other ideas.

Glenn, do you know anyone who has done this?

Edit: Bigger? I know how to do that!!!!

Thanks,

Jeff

 

[Terry Keeley]

Olly,

On the wrap around motor that we run, we have not had any issues with the stock carb drawing fuel. Our carb has the low end needle cut out of it as well and we run standard medium size dubro fuel line. Check the seal bores between the bearings. Does the exposed bearing on the rotor have a seal on it?

Andy might be on to something as well. I had this problem on my scale a while back where it would quit running after 5 or 6 laps. I ended up fixing the fuel draw problem by reducing the stinger size on the pipe.

Ok, if the DD engine is having the problem and the wrap around engine did not, then the other problem could be the PTO seal. Some of you guys know that Rod G. was adamant about the importance of the PTO seal on OB engines. Maybe Nova did not pay close attention to that detail.

Even so, a bigger spraybar bore, (about .100") for better fuel delivery and a bigger stinger diameter (about .420") to let the heat out would cure the problem, even with a poor PTO seal. That combination will let the engine idle cleanly on the beach with less than half throttle and the engine will get the fuel it needs under a load.

Wouldn't a bigger stinger make less pipe pressure and cause a further lean condition?

Really think the thing is suckin' air somewhere...

 

[Jeff Schindler]

Wouldn't a bigger stinger make less pipe pressure and cause a further lean condition?

Really think the thing is suckin' air somewhere...




Can you snorkel the carb about 6 inches away from the engine and spray some brake clean around the running engine?

If it goes rich and dies then there is a leak. I worry though that the brake clean is robbing the bearings of lube, but I have tried this before.

 

[Elias Vazquez]

I can't find any cracks in the motor. Do those of you with Frank Orlic carbs have this problem? I am trying to narrow it down to a motor or fuel problem.

Thanks

Olly

No problems with the Frank O. Carbs. Couple of the guys over here run the stock carb without any problems, but one of them did find one of the o-rings that seals off the needle to have been dry and cracked right out-of-the-box when he went to cut off the low-end. These are four 46DD running in riggers with no issues...two w-stock carbs, two w-Frank O. carbs.

Good luck finding the culprit!

 

[Olly]

Mike, the exposed bearing does not have a seal on it so perhaps this is part of the problem. I've put less than a gallon of fuel through it so I wouldn't have expected a bearing problem. I'll look at that next.

 

[Tim Kish]

Would be nice to have a small pressure gauge to run off the pipe pressure to compare with a standard motor .

I believe because of the design there is more surface area to try and seal

and its leaking pressure out of the PTO .

 

[SayMikey]

Olly how much water are you running to motor

 

[Olly]

Mikey

I have no restrictions in the lines.

Olly

 

[shoboat]

Jeff,

The easiest way is use K&S brass tubing and flare one end and drop it in the pipe

and use a little JB Weld to hold the outside seal on the pipe.

Have Fun Testing Jeff,

Mark Sholund

 

[Tim Kish]

We have tried reducing the stinger, also full water no restriction at all and choked down to what we typically run.

Definitely not a heat issue .

 

[Andy Brown]

Olly,

On the wrap around motor that we run, we have not had any issues with the stock carb drawing fuel. Our carb has the low end needle cut out of it as well and we run standard medium size dubro fuel line. Check the seal bores between the bearings. Does the exposed bearing on the rotor have a seal on it?

Andy might be on to something as well. I had this problem on my scale a while back where it would quit running after 5 or 6 laps. I ended up fixing the fuel draw problem by reducing the stinger size on the pipe.

Ok, if the DD engine is having the problem and the wrap around engine did not, then the other problem could be the PTO seal. Some of you guys know that Rod G. was adamant about the importance of the PTO seal on OB engines. Maybe Nova did not pay close attention to that detail.

Even so, a bigger spraybar bore, (about .100") for better fuel delivery and a bigger stinger diameter (about .420") to let the heat out would cure the problem, even with a poor PTO seal. That combination will let the engine idle cleanly on the beach with less than half throttle and the engine will get the fuel it needs under a load.

Wouldn't a bigger stinger make less pipe pressure and cause a further lean condition?

Really think the thing is suckin' air somewhere...

"Wouldn't a bigger stinger make less pipe pressure and cause a further lean condition?"

ABSOLUTELY! That is why the spraybar bore MUST be increased at the same time. You can't correct just part of my above stated equation. The complete equation must be correct.

I am currently running an OLD CMB 100 with a .500" stinger bore. The engine idles perfectly, starts on the first pop and Never burns plugs and runs in the high 80's. To go with that BIG stinger bore it has a BIG spraybay bore. Also, the engine is almost 20 years old and the bearing housing seal is wore slap out. It leaks so bad that the engine bay is covered in oil after just a few runs. Shaft seal is not that critical if the spraybar is the correct size (big enough).

 

[aaron alberico]

Stock stinger bore on NR pipes should be .393 out of the box... Which should be big enough...

Regards Aaron

 

[John Beardslee]

Hi Aaron,

I've got two of the muffled pipes like Olly is running and both have stinger I.D.'s .353 -.358 never seen one with that large bore.

Thanks, John