boat not running right

[davo]

Hi

I spent most of sunday down at a lake with my .67 sprintcat. We threw it in and it went really well. after a few laps it stopped so we went out and got it. We didnt change anything and we threw it in and it didnt "hop up" on the pipe at all. We then leaned it off a bit and put it in and done the same thing. We richened it right off and it took the whole straight to get on the pipe so we thought we had to richen it up more and same thing.

P.S the prop is a prather 245 and 15% nitro.

Dave

 

[westoz]

Gday Davo try a higher nitro mix perhaps 40-50% and ensure fuel system is pressurised correctly what size tank using.

 

[gil sonsino]

Sounds your pipe is too short ! Start at 11" and make sure the rest is absolutely ok ... I mean ..... height of the strut,lenght of the pipe,airleakage in your line are things to be checked carefully not to forget the plug and fuel.

Gill

 

[Pennywizz6]

This happened to me before and the problem was water found its way into the carb! If it hasnt happened before its probibly not it, but you can just double check.

Phil <_<

 

[davo]

the thing that gets me is that it went really good and we changed nothing and it then went bad. It was on the bank for about 2 minutes in betweeen it going good and bad. The tank is a sullivan bt-16. I dont think it will be to low nitro because it went alot better on 10%. I dont think it was water in the carb because the cowling was on during the run and it wasnt raining at all.

P.S the hull is an aeromarine sprintcat 36' and a 1 yr old cmb .67 bought new if this info helps

 

[davo]

bad bearings perhaps???????

 

[Don McMurchy]

Like Gill said it sounds like your pipe is to short.

 

[gil sonsino]

Have you checked the position of your pipe after things turned bad? Sometimes the pipe moves from its original position and can cause all this trouble.Water in a cat even without a cowl is something rare to happens but all possibilities must be considered.How is your silicone coupler...cause any leakage here will kill your engine!Is this CMB equipped with two needles(low and high)?.Also verify if your Zimmerman valve(rear disc) is sealing well the back plate!

Hope this help.

Gill

 

[catman]

goop in the pressure fitting?

hey, im no expert, But ive had heaps of the same problems in the past, check to see your pressure nipple in the pipe is not blocked, change the plug, make sure your fuel system is holding pressure, the best way i found was to sumberse the tank in water, block off the outlet and blow into the pressure line. make sure no bubbles are escaping. Also make sure your needle valve doesnt have any goop in it.

Good luck

 

[TimD]

Split pick-up tube in the tank?

Fill the tank back up to the top - does it behave again until the level drops down? Draining the tank with an electric pump usually shows this up - airated fuel coming out of the pump.

Pressurise the whole fuel system with air thru the exhaust line in a bucket of water and look for bubbles.

Tim.

 

[EatMyShortsRacing]

Guess number 43....

Your plug went south......

EMS Racing Best guess for your $0.02

 

[westoz]

Try installing a small 1 or 2 oz hopper tank about level with carby should get a constant fuel flow.

 

[davo]

The pipe is at 11 inches before and after the run. Ow hang on , i just checked the plug and all the coils are out of line

BINGO?????????

Still not telling us why it went better later on in the day.

 

[gil sonsino]

HI Davo

Once the first clue is here ...the bad plug.....check your head clearance that must be at 0.013 and keep the rest untouched.If the problem repeats itself check the bearings .How is the aspect of your head and top of piston.... too much sandblasted?This is a sign sometimes related with bad h.c. or engine too lean.By the way safe your plugs running more rich!.

Good luck

Gill