1972 25 hp Rude no top end power

[69 Alumacraft]

Compression 120 on both new fuel pump, new plugs, spark jumps a mile on tester. Has to be the carb right? Rebuilt year before last and it runs great at idle but weak top end and tons of unburnt fuel coming out of LU. In the past my carb problems equaled bad idle so I figured carbs are still good because it idles great. Someone tell me to clean the carbs again.

 

[boobie]

Clean the carb again and especially check the high speed jet in the float bowl.

 

[F_R]

So, has somebody "cleaned" the high speed jet (oifice plug) with a drill, wires, or torch tip cleaners? Or has somebody installed a larger jet with the crazy idea it would go faster if it gets more gas? (It won't). That is a precision hole through that jet, not to be messed with except carb cleaner and air.

BTW, idle fuel is metered by the adjustable needle, high speed fuel is metered by the high speed jet.

 

[69 Alumacraft]

I disassembled, cleaned with carb cleaner and compressed air a couple of seasons ago. I have since changed boats form a 14ft Alumacraft to a 13 ft Whaler. I know the whaler is much heavier but I expected better performance and the loads of unburnt fuel is new. BTW I also did a seafoam decarb and replaced the plugs after. Bu t it had excessive fuel sludge before the decarb. I will tear down the carb and see what happens. I don't think I am going to pull the low speed needle gasket out since idle is fine.

 

[Sirrobin53]

Almost sounds like needle and seat. At idle, runs fine but engine vibration at higher R's keep it open.Just a thought. Didn't change prop?

 

[racerone]

Fuel pump diaphragm ruptured ?

 

[69 Alumacraft]

Changed prop and put in new Evinrude not Sierra fuel pump.

 

[Sirrobin53]

Higher pitch prop or the same?

 

[69 Alumacraft]

I think it is the same, going to test it out today. I will post back.

 

[Sirrobin53]

I bought a new fuel pump that didn't pump enough. Tried to save $$ on a cheap one. Got BRP and Wa La. I was in tall cotton again

 

[69 Alumacraft]

I have come to the conclusion that it is the weight difference between the alumacraft and the whaler. When I moved some weight forward it plained out. 68 Whaler with deep cell battery, 6 gallons fuel, trolling motor, 240 LB man all in the back. Once I moved stuff forward it plains out. After carb cleaning less goop coming out of LU. I have a 30 hp E-tec on order so just have a couple of weeks left with the 1976 25 hp.I am expecting better performance. Thanks to all. If anyone disagrees please post.

 

[69 Alumacraft]

Now it is making loud exhaust noise after wot for 5 minutes or so almost like running it out of the water. Thermostat ? If I slow down and start again it goes away but comes back later. Only happens at WOT with a full load, with just me it does not happen. No noticeable change in performance?

 

[69 Alumacraft]

Anyone?

 

[racerone]

How high is the transom ?----Picture of motor installed on the boat??

 

[69 Alumacraft]

It is on a 1968 13 ft Whaler with a 15 inch transom, the motor definitely matches the boat.

 

[Chinewalker]

I've had this a few times. It is just the exhaust venting to the air. A disturbance in the water breaks the surface tension as the motor is running and then once broken, it stays that way until you come off plane and dunk the exhaust again. Seems to happen with the 22-cubers more than others, I've noticed... Nothing to worry about.

 

[Sirrobin53]

My 18 does it also. When it does I always check to see if it is still pumping water and it is.

 

[tblshur]

69 really sounds like prop needs to be deeper or trimmed a bit . good luck

 

[69 Alumacraft]

Thanks guys. Got a "Dolefin" from Davis instruments.I have another 70's Johnnyrude that runs good, just trying to pick one victim to drill into cav plate.