carb adjustment, 70' rude 25hp

[clemsonfor]

I have been reading over the forums on iboats for several weeks with the purchase of a new boat. <br /><br />Anyway the motor is a 70' rude 25hp.<br /><br />I just had carb rebuitl abter it quit running.<br /><br />when i first put carb on boat and started it started right up which it would not do before it was rebuilt. It sounded like it was missing though. When i took the boat out it would not plane and motor seemend only to be at half throttle even though it was at WOT. Then the motor cut off and could not get it restarted. after i put it back on trailer i saw the throttle linkage fell off so i pu that back on and it would not start. I know the boat is faster than it is b/c i ran it for seval hours after getting it with no problems.<br /><br />Also i have spark on both cyl. and fuel pump is pumping.<br /><br />i have looked for old post on the carb adj. but could not find any that i knew were a similar motor.<br /><br />If you don't mind could anyone let me know the correct adj procedure for this boat.

 

[Joe Reeves]

Re: carb adjustment, 70' rude 25hp

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)<br />(J. Reeves)<br /><br />Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.<br /> <br />Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.<br /> <br />Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /> <br />Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.<br /><br />When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[Catwagon]

Re: carb adjustment, 70' rude 25hp

I needed that info too! Thank you very, very much Mr. Reeves.<br /><br />Steve

 

[clemsonfor]

Re: carb adjustment, 70' rude 25hp

got the slow spped adj. After figuring out there was a fixed hig speed. But now when at WOT is seems the motor is only getting 1/2 to 3/4 throttle. <br /><br />I have good gas, spark, swapped tanks and primer line to known good ones, am hitting on both cylinders as when at WOT if i pull 1 at the time it cuts back. Yes, the linkages are hooked up correctly, when stopped or underway i can watch the cam follower move up to the WOT position. Fuel pump worked before the high speed jet was clogged requiring a rebuild and yes the boat went faster than it does now also before rebuild. Also while under way pumping bulb does nothing.<br /><br />Motor ran fin until jet got clogged. I know that was the proble b/c before rebuld when pulling the drain screw on card very little gas would trickle out now it pour out when pulled.<br /><br />I did not do the rebuild myself (father in law did). I pulled it for him, he also is a auto mechanic not a boat mecan. Were looking for help here.<br /><br />What should we look for in the internals of the carb that could be causing this problem.<br /><br />Thanks<br /><br />-Nate

 

[Silvertip]

Re: carb adjustment, 70' rude 25hp

Make sure the choke is working properly. Then ensure the throttle plate in the carb is opening all the way. At wide open throttle it should be parallel with the throttle bore -- no more, no less. If it is not opening all the way, link & sync needs to be done. When that's done, if this is a remote controlled engine, make sure the throttle cable is properly adjusted. Sounds like you should also get a service manual specific to your engine as link & sync is far too detailed to go into here.

 

[BF]

Re: carb adjustment, 70' rude 25hp

I've also got a '70 'rude 25hp... I have the factory service manual, but not in front of me. I remember the link and sync isn't complicated on that motor. The carb butterfly should only start to open after the roller has passed the marks on the cam. loosen the set screw that tightens on the butterfly cross shaft to adjust as needed.<br /><br />you might also wanna check compression if it was run with a partially clogged carb...<br /><br />good luck

 

[clemsonfor]

Re: carb adjustment, 70' rude 25hp

The motor is tiller steer. The butterfly opens all the way. I have checked that. I am looking for manuals on the internet(ebay and other sites to get a deal). Right now all i have is the service manual that coves that adjustment, but like i said i have thought about that and it is not a problem. This manual is a omc "Service manual" It is very general an not to detailed. Have not checked comp. yet. BUt motor ran fine untill jet clogged and then almost imediatly cut out, then i sprayed jet out and it ran for about 15min then stopped sudden again, then carb was pulled for rebuild.<br /><br />I also thought to put back all the original parts into the carb as it was just the jet that was clogged, and it again seems to be only operating at 3/4 throttle.<br /><br />-nate

 

[BF]

Re: carb adjustment, 70' rude 25hp

my point is you don't know exactly when the jet started to clog, you just know when the motor quit... It was running lean for some period of time, and now it's not running right. If it were me, I'd do a compression test next before trying to tweak/tune a motor that might have bigger problems.<br /><br />that's my $.02

 

[clemsonfor]

Re: carb adjustment, 70' rude 25hp

i see what you mean now.<br /><br />Thanks<br />-nate

 

[clemsonfor]

Re: carb adjustment, 70' rude 25hp

Ok, problem solved. Looked at OMC site and got parts diagram for carb. Saw a part on the diagram that i do not remember in the carb, but remembered in the rebuild kit. Turns out the old float bowl gasket was a 1 piece and the new one was two, one on the outside edge of float boal and a little rubber washer around the venturi tube inthe center of bowl inside the middle of the float. Put it back togeather with this rubber gasket washer in place and problem solved.. The problem was that it was sucking in air the air was coming from inside the carb with this little gasket missing! <br /><br />Thanks for all y'alls help.<br /><br />-nate