stumped!?!?!

[unknown_sender12]

Alright hopefully somebody can figure out whats going wrong so i can catch most of summer. My boat ran fine for the for about the first 6 rides, then i put a new prop on and about 2 rides after that i start having problems. As a side not i never run my boat higher then 5100(except if im trying diagnose) I got an 87 200hp envinrude. It idles great and run great at high speed. The high speed for it now is about 200 rpm lower than it used to be. My main problem is that whenever i try to get the boat to plane it will run fine up until it hits 2500rpm then it will just bog right out and start running rough. I tried pumping the primer ball and it did nothing, tried pushing the key on to engage choke and it really bogged the motor, we tried spraying premix into each carb when the motor was bogged and it had little to no effect. When i sprayed in the carbs most of the time it bogged the motor a lil or you would just hear the engine bog such a small amount that you could only slight change in sound. But when we sprayed into the top carb on the port side the engine revved up about 100rpm. When on shore i took the hose off of the outlet of the fuel pump cranked the motor for a few seconds, it delivered a constant amount of fuel and we let it pump about 8 times. I pulled all the plugs and all of them delivered a crisp blue spark and are gapped to .040. THis whole time im thinking the carbs need to be cleaned or rebuilt but im trying to avoid it. I also went on the water this evening to check the timing. In my book it says pick up timing should be 5-8 BTDC and advanced timing a WOT should be 17-19BTDC. so i took it out on the lake and my idle timing is 6 ATDC i cant even get in to go to TDC, My advance timing at 5150rpm is 7 BTDC. I played with that to and cant get it anywhere near 17 but my rpm at WOT went from 4900 to 5150, So i dug a little deeper and turn out because of some repairs back in the day i now has a flywheel off of a 86 250hp. I used a dial indicator to figure out where TDC starts and finishes. then went halfway in between, and put a mark on the flywheel, it was at about 3BTDC according to the flywheel. So what do i do.

 

[tashasdaddy]

Re: stumped!?!?!

sounds like carb and link & sinc problems, like the one carb is not delivering, which can damage the motor as it is not getting lubrication. did you change pitch when you went with the new prop?

 

[unknown_sender12]

Re: stumped!?!?!

nope same numbers on this prop as my old one just my old one had been rebuild and whoever did it did a terrible job as it would cavitate anytime i tried to get out of the water, what do you mean link and sink problem, you just mean worn linkages?

 

[Silvertip]

Re: stumped!?!?!

Link & Sync is the process of synchronizing spark advance with carburetor throttle opening. This is rather lengthy procedure and is far too detailed to go into here so you really need a service manual for your engine to do that properly. If you have one carb that is not synchronized with the others, it may not open (or close) the same as the others. One quick test would be to remove the air box and move the throttle lever on the control box full open. At that setting, the butterflies in each carb should be perfectly horizontal in the carb bore. Any that are not horizontal (open too little or too far) means you need to do a link & sync. If none of them are open fully, but they are all open the same amount, then it may be just a cable adjustment issue.

 

[mikesea]

Re: stumped!?!?!

well,as for the timing,the eng ran fine for along time with the timing as it was,hopefully you didn't change it so drastic that you end up dentonating a piston ,which wads a common problem,the 250 hp engines had 8 cylinders,the 8 cyl flywheel wont work.You could be losing a coil at higher rpm,be sure to check all connections,especially grounds and plug in pin connections,you might want to CAREFULLY,with someone else running boat.do a simple load test while underway.pulling each plug wire and see which Cyl(s) are effected,you might have a key switch goin bad ,throwing ground to the kill circut,you can unplug the yel blk kill wires from the pack ,see if you get any reaction,only getting 100 rpm at wot shooting fuel into the carb.doesnt get you a full cyl result,I doubt the carb is the problem,the prop would have nothing to do with it because you had successful running when first changed,let us know if you find the answer,Im curious

 

[unknown_sender12]

Re: stumped!?!?!

well the carbs arent the problem i rebuilt them and there is no difference. i checked with my timing light to make sure i was getting a spark to all cylinders when it was bogging out. if i hook a gauge up to my fuel pump what kind of numbers should i be expecting?

 

[unknown_sender12]

Re: stumped!?!?!

i lent my new prop to my uncle and he also has a 200hp a couple years older. He started having the exact same problems, his motor would bog right down and couldnt get on top of the water, well i got my old prop back and threw it on for ****s and giggles and now the dam thing runs fine, that prop cavitats like a bastard but the boat can get itself out of the water...(i pulled a 3 man tube this weekend and no one on it was lighter then 160lbs took a some creative driving to get planning though) if i remeber correctly the first two days i used my new prop it was quite choppy out.so maybe that lil bit of wave helped lift the boat out of the water. so now i have a prop that i cant use and cant return, does anyone know if i brought it to a machinist and got it ported if it would be enough to help get my boat of the water. also what size of prop do yall figure i should run. im usually pulling a tuber sometimes skis, both of my props are 14 1/4 X 21. my old one was rebuilt before i owned it and the blades look like they were shaved down a bunch when comparing it to my new prop (almost an inch diffence in radius of prop)