Any Ideas

[nitronewbie]

I'd like to run this one by you guys, my 1/8 scale-- mac 67 powered with a walt barney fuel tank, CMDI third channel valve, CMDI Brown 67 pipe set at 11" (plug center to seam lenght) turning a Prop-4-you 455/3, 457/ 460/2 does not matter, and 50% rich's brew fuel (this yrs)

Running it rich enough that I've got fuel running out the pipe. drop it in the water and it will take off down leg pulling good. Turns 1 & 2 pulling hard and sounding ok, half way down back straight it shut off ( just like someone turns the fuel off ) retrieve the boat and it fires right back up. plug still good, Do it again and the same thing, pulls turns 1 & 2 and quits down the back straight. I changed a couple weeks back from a BV third channel valve to the CMDI. I've had the fuel tank out twice washing it out the best I can. the motor was new last spring and is bone stock (less than 1 gallon through it) I"m lost ???

second question for you guys--I've got new bearing for it (don't really think old one were all that bad)

How do you get the inner big bearing out???

Thanks John

 

[Don Ferrette]

I'd like to run this one by you guys, my 1/8 scale-- mac 67 powered with a walt barney fuel tank, CMDI third channel valve, CMDI Brown 67 pipe set at 11" (plug center to seam lenght) turning a Prop-4-you 455/3, 457/ 460/2 does not matter, and 50% rich's brew fuel (this yrs)

Running it rich enough that I've got fuel running out the pipe. drop it in the water and it will take off down leg pulling good. Turns 1 & 2 pulling hard and sounding ok, half way down back straight it shut off ( just like someone turns the fuel off ) retrieve the boat and it fires right back up. plug still good, Do it again and the same thing, pulls turns 1 & 2 and quits down the back straight. I changed a couple weeks back from a BV third channel valve to the CMDI. I've had the fuel tank out twice washing it out the best I can. the motor was new last spring and is bone stock (less than 1 gallon through it) I"m lost ???

second question for you guys--I've got new bearing for it (don't really think old one were all that bad)

How do you get the inner big bearing out???

Thanks John

First question, can you see good water spray out of water outlet when she goes off in the water? :blink:

Second question, is water getting under the cowl? the MAC carbs tend to sit right at cowl to deck level on scales. :huh:

 

[Lay26]

next question is what size is the fuel lines and is the brass from the tank 1/8 or 5/32? you may have a fuel draw problem. my 2 cents

 

[Shark]

Nitro,

before you replace bearings, first you need to isolate the problem.

On the third channel, take it apart and see if there is any debris in the valve that may cause blockage at full throttle. After inspection, if it looks ok, take it out. Run a remote manual needle and see if the condition continues. If it does, you have a pressure problem.

Second, check your radio to see if there is any interference or maybe a throttle servo shuting down on you at a certain spot on the track. (seeing that you said its dies in a similar place)

Range loss will make your servos go to another position as they search for a signal.

Third, check your coupler for a good seal, with heat, the coupler will expand and possibly casue a leak which will lean you way down and shut you down.

Fourth, as Don said, maybe you are retaining too much water and its getting in the carb. try a piece of absorbing foam beneath the engine yet below the carb to soak up the water and test it again.

If all these isolation drills fail, then you can look to the engine for answers.

the bearings can be removed by using a propane torch heating the case around the bearing housing and lightly tapping the case on a surface and the bearings should just drop right out

Internally, I would check the rod for bends as this will cause the same condition. have you fliped this boat or engine while its was running?

Just my opinion.

Rey G.

 

[Don Ferrette]

Rey makes a good point about a glitch in the throttle servo. My Smokin' Joe's scale had weird stuff happen to it at Springnationals back in April. It ran great on Friday open water for the TV news crew but never ran right after that, typically going 100 yards & quitting which also cost me one very nice Concours trophy. Once I had it back on shore it would fire right up. Next time out a couple weeks later it did exactly the same thing, ran great one time then wouldn't go but would fire right up on the beach. I was goin' nuts to the point I was going to switch motors. Back in the shop I was going to pull the motor & when I went to check the radio trim settings before I switched out the motor I found the throttle servo was toast! Replaced the throttle servo & boat has run fine ever since. :huh:

 

[EatMyShortsRacing]

I'd like to run this one by you guys, my 1/8 scale-- mac 67 powered with a walt barney fuel tank, CMDI third channel valve, CMDI Brown 67 pipe set at 11" (plug center to seam lenght) turning a Prop-4-you 455/3, 457/ 460/2 does not matter, and 50% rich's brew fuel (this yrs)

Running it rich enough that I've got fuel running out the pipe. drop it in the water and it will take off down leg pulling good. Turns 1 & 2 pulling hard and sounding ok, half way down back straight it shut off ( just like someone turns the fuel off ) retrieve the boat and it fires right back up. plug still good, Do it again and the same thing, pulls turns 1 & 2 and quits down the back straight. I changed a couple weeks back from a BV third channel valve to the CMDI. I've had the fuel tank out twice washing it out the best I can. the motor was new last spring and is bone stock (less than 1 gallon through it) I"m lost ???

second question for you guys--I've got new bearing for it (don't really think old one were all that bad)

How do you get the inner big bearing out???

Thanks John

My 67 Hummingbird was doing that but taking the plug out too... was way too lean due to a drum problem. Once I fixed the drum I found a similar problem which was still from being too lean BUT the plug survived. Was using a MACS pipe then so have decided to go to the AB pipe but have not been able to test since....

From AB referring to motor going into 'lean bog'...

"It is just starving for fuel. He has the "In-line needle", not the third channel, so he's good there.

The only problem is the full bore (.470") stinger on the AB 67 pipe (black). He's trying to run in cool weather (good air), so he needs more stinger restriction to deliver more fuel. Get a .410" or .430" bushing in there then tell us how it runs."

 

[ALLAN YUEN]

I'd like to run this one by you guys, my 1/8 scale-- mac 67 powered with a walt barney fuel tank, CMDI third channel valve, CMDI Brown 67 pipe set at 11" (plug center to seam lenght) turning a Prop-4-you 455/3, 457/ 460/2 does not matter, and 50% rich's brew fuel (this yrs)

Running it rich enough that I've got fuel running out the pipe. drop it in the water and it will take off down leg pulling good. Turns 1 & 2 pulling hard and sounding ok, half way down back straight it shut off ( just like someone turns the fuel off ) retrieve the boat and it fires right back up. plug still good, Do it again and the same thing, pulls turns 1 & 2 and quits down the back straight. I changed a couple weeks back from a BV third channel valve to the CMDI. I've had the fuel tank out twice washing it out the best I can. the motor was new last spring and is bone stock (less than 1 gallon through it) I"m lost ???

second question for you guys--I've got new bearing for it (don't really think old one were all that bad)

How do you get the inner big bearing out???

Thanks John

What kind of 1/8 scale model? h34r:

 

[SayMikey]

I'd like to run this one by you guys, my 1/8 scale-- mac 67 powered with a walt barney fuel tank, CMDI third channel valve, CMDI Brown 67 pipe set at 11" (plug center to seam lenght) turning a Prop-4-you 455/3, 457/ 460/2 does not matter, and 50% rich's brew fuel (this yrs)

Running it rich enough that I've got fuel running out the pipe. drop it in the water and it will take off down leg pulling good. Turns 1 & 2 pulling hard and sounding ok, half way down back straight it shut off ( just like someone turns the fuel off ) retrieve the boat and it fires right back up. plug still good, Do it again and the same thing, pulls turns 1 & 2 and quits down the back straight. I changed a couple weeks back from a BV third channel valve to the CMDI. I've had the fuel tank out twice washing it out the best I can. the motor was new last spring and is bone stock (less than 1 gallon through it) I"m lost ???

second question for you guys--I've got new bearing for it (don't really think old one were all that bad)

How do you get the inner big bearing out???

Thanks John

What kind of 1/8 scale model? h34r:

Run it without the cowl,you may be choking the carb inlet. Also what kind of radio are you using could it be a fail safe loosing signal,i saw a m11 do it and we like to never figured it out

 

[nitronewbie]

Thanks for all the replys---first off i'm running 5/32 fuel lines I understand MAC's like lots of fuel, second I did replace a throttle servo saturday morning, it was toast ( did not get any good runs sunday as the pond was very rough) thirdly I did restrict the cooling line (on one run it quit right in front of me, no more than 10 seconds to get cowl and the head was stone cold ) I've had both my BV and CMDI third channel valves apart and have seen nothig in them?? I did get my bearing out today and will replace them. Hoping to get to the pond on wednesday and retry Thanks guys John

ps --I'm running a Phil Thomas T-5 Miss Budweiser Hull

 

[P THOMAS]

Thanks for all the replys---first off i'm running 5/32 fuel lines I understand MAC's like lots of fuel, second I did replace a throttle servo saturday morning, it was toast ( did not get any good runs sunday as the pond was very rough) thirdly I did restrict the cooling line (on one run it quit right in front of me, no more than 10 seconds to get cowl and the head was stone cold ) I've had both my BV and CMDI third channel valves apart and have seen nothig in them?? I did get my bearing out today and will replace them. Hoping to get to the pond on wednesday and retry Thanks guys John

ps --I'm running a Phil Thomas T-5 Miss Budweiser Hull

MIKEY TOLD YOU TO CHECK THE COWL

IF YOU USE THE MAC AND HAVE NOT TRIMMED THE COWL BULKHEADS HIGHER IN THAT BOAT THE MAC CARB CAN BE RESTRICTED AND THE MOTOR WILL NOT RUN RIGHT. THE CARB SITS RIGHT WHERE THE JOINT IS BETWEEN THE DRIVERS COCKPIT AND THE CENTER COWL..

PHIL