Help with poor runing boat

[anthony_marquart]

i ran my Sp21 Sat and hot a ton of trouble.

Set up:

AJM SP21,.. proven design,.. has always run well

NR5p

AB parobolic pipe

65% fuel

tried various props that all worked before

The boat would get on the pipe but never really spool up.. needle down a bit and die..

Always launched well,.. only died at a leaner needle,.. right after getting on the pipe..

I'm thinking bearings.. compression seems good still.

What do you think?

Ok,.. Ill add the funny part.. The boat had died in a bad spot on the lake.. dead calm.. now leaning against the fountain,.. I find a blow up raft in the little shack that has the grill and stuff in it.. I blow up the raft (with my mouth) and paddle out to the boat.. That is when I realized there is a hole in this raft.. paddled back in a hurry.. all is well.. better than a good day in the office

 

[TimothyJones]

How does the plug look after leaning down?

I had that same problem,I thought bearings too and found the head clearance was too tight.

The plug looked good as long as I ran rich, lean it down....boom..blown plug

 

[anthony_marquart]

Plug was good the whole time.. changed out the plug during the testing just in case it was that.. Plug was frosted over,.. looked real good actually..

I also reduced and then increased the water flow.. still no change..

I may put the NR Hybrid I have in it just to rule out all the other possible variables.

 

[Brian Sorgente]

My first thought is bearings. When they start doing funny stuff like that, especially if everything looks fine, typically its time for a new set.

Brian

 

[anthony_marquart]

I think Glenn is on holiday.. does anyone know where to get the NR 5p bearings?

 

[Bob Kensill]

John Otto should have them. You didn't give the numbers of the props you tried. A detongued Octura X440/3 prop worked best on my Phil Thomas sport 21 hydro

 

[anthony_marquart]

thx Bob,.. Ill contact John,.. The props where a MS x442, an ABC prop I cannot remember, both done by mark,.. a P220,.. and a x440.. all have run pretty good in the past,..

 

[anthony_marquart]

NO more input? Come on guys.. I need to have a better day at the lake this weekend!

 

[mtruex]

Air leak or trash in needle...

 

[David Santistevan]

Bearings would be my first guess, Rob Holland was the one that told me that anytime you start chasing a needle to check your bearings after checking the obvious like leaks in the fuel line, loose fittings or needle.

D

 

[anthony_marquart]

thanks guys.. I'm getting some bearings.. I flushed out the needle at the lake.. one thing about the simple hand crank fuel pump,.. you can hook it to the needle and flow back and forth with some pressure to flush out the crap..

Thanks again..

 

[gooycheese]

make sure your pressure line from the pipe to the tank is good also and no blockage at the fitting in the pipe

 

[rick lindow]

Anthony, make sure your pipe seal at the header is good, pressure fitting on pipe, coupler is good, pressure check all tubing and test tank for leaks make sure pipe hasn't moved (mtr. tear down and inspect) recheck head clearnce! lots to look at, good luck! Rick L.

 

[gooycheese]

i am guessing sullivan tanks? Make sure they are leak proof. the waterline fitting on the jacket is tight correct, no water is misting into the carb?

 

[HOTWATER]

Also make sure the copper washer for the plug is good. Had the same problem as you one time and simply put a new plug washer on the plug...problem was gone instantly!!! Was an air leak like Martin suggested in his post above....

-Kent

 

[anthony_marquart]

i am guessing sullivan tanks? Make sure they are leak proof. the waterline fitting on the jacket is tight correct, no water is misting into the carb?

No,.. Custom plastic tanks from Ryan,.. but Ill check them all,.. easy enough to blow through all that as hard as I can and see if anything moves or makes noise..

Im thinking it might be the orings in the needle. never have changed them,.. Ill check that too..

oh, and the water pressure on front the pickup is vented out the back of the rudder blade. most the pressure bleeds off there. it flows a small stream for cooling.. not much pressure on the water lines in the head..

Thanks

 

[Bert Dygert]

Anthony,

Check your header coupler for small pin holes or splits. I had that problem on my 20 hydro over the weekend( split the coupler) losing back pressure for the fuel system. If your running dual tanks check your fuel lines for pin holes.

Regards,

Bert Dygert

 

[dave roach]

I know on my sport 20 that it has to be real rich on the bank.All good points here.

Dave

 

[anthony_marquart]

Well I have it all apart. I found a couple things

- the bearings seem pretty good. Very smooth and quiet. But the big bearing has some axial play. Just a little maybe 0.025. Do you think that is enough to cause this problem? Not sure if this is really an issue.

- I found a cracked exhaust gasket between the case and the header. I'll replace it.

- There is less than .002 play between the crank pin and rod. It does seem to have a lot of play with the motor at TDC. Maybe 15 degrees.

-there are very very light swirl marks on the back plate. Very light and way less than I have seen on other engines.

- all tanks and lines seem to hold air. I cannot blow air into them and make them leak.

Wondering if I should change the bearings or not.

What do you think guys

 

[David Murany]

Was the weather really hot and humid? Had a problem where I couldn't pull my normal props very well so I propped down and boat ran ok. Just wasn't making the power with warmer Temps than earlier in the year.