HELP!! engine stops as soon as it takes a load

Help!!!.70 hp envirude works fine in and out of gear when it is on the water cups. As soon as i put it in the water and put into gear, it cuts out when any throttle given. Weird one for sure.

Re: HELP!! engine stops as soon as it takes a load

Take a compression test, guess you are at least one cylinder out.
Start with compression test, then verify with ignition tester that you have spark to all cylinders.

Re: HELP!! engine stops as soon as it takes a load

Thanks Haffiman, One would think though that if a cylinder is not working i wouldnt get nice smooth acceleration and throttle when it is on the cups. I wonder if the load is throwing out the timing?

Re: HELP!! engine stops as soon as it takes a load

No back pressure and no load, it might even run on one cylinder.
Timing is 'mechanical' and not related to load.

Re: HELP!! engine stops as soon as it takes a load

Thanks Man, I did put threee carb kits in it yesterday. So how do you check for compression? and what should it be?

Re: HELP!! engine stops as soon as it takes a load

ouch- this sounds like my motor. Idles great but bogs down under load.

Re: HELP!! engine stops as soon as it takes a load

Does it bog down or completely stall out when it's put under load? Try the "usual suspects" (carb cleaning, link-n-sync, check spark and compression)

Re: HELP!! engine stops as soon as it takes a load

wow... well.. please tell me you did a sync and link when you reinstalled the carbs??? the sync and link is extremely critical for proper ignition timing per throttle plate opening and to load.

and yea, you really need to check compression. JohnsRude's are notorious to run "smooth as a new" with a dead cylinder on the hose.

to check compression you need to have a gauge that goes in the cylinders. Set the throttle plates to full throttle(manually), remove the lanyard, and crank the engine... you should get a reading around 110 to 145PSI. (in that ball park) the main thing you need to look for is a drop or difference over 15% between the cylinders. All the engines I have worked on that have a dead cylinder or 2 is usually VERY noticeable. Like 115psi in cyl1 and 32psi in cyl2.. or something like that.

Re: HELP!! engine stops as soon as it takes a load

I have the same exact situation, but with a big twin- and right now I am looking at something as simple as a fouled top plug.

Re: HELP!! engine stops as soon as it takes a load

My 65 HP did the same thing. It ran great on the muffs at home, but when I put it in the water, the fast idle lever wouldn't make it idle very fast, and when I would shift it into gear and try to give it throttle, it would just die. When I got it home, I pulled the bowl plugs on the carbs and I could see that the high speed jets were all completely plugged with gunk that had been in the float chamber. A good overnight soak in carb dip will do wonders. You said you did carb kits, but did you soak the jets and carb bodies with the core plugs removed? Ever since I did that, my motor idles like a dream, and has full power at takeoff.

Oh, BTW, which motor are we talking about here? Please post a model number.

Re: HELP!! engine stops as soon as it takes a load

You can buy a compression tester and a spark tester at an auto store like napa or harbor freight for cheap. Compression tester screws into the head in place of the spark plug. Spark tester gets the plug wire plugged into it instead of the spark plug. It really does sound like you're short a cylinder.

Details on both tests here:
http://forums.iboats.com/showthread.php?t=299680

Also try the cylinder drop test- get it running on the muffs and remove one spark plug wire at a time and see if each one makes a difference. If you pull a plug wire and it doesn't bog down you've got some sort of problem (fuel/spark/compression and maybe all 3 are there but one is a bit off) with that cylinder.

Since you just did the carbs they're probably ok and at least worth moving past for the moment for these two tests. Follow the directions in that thread and post the results here for all cylinders and both tests.

Also did the motor ever work well for you or did you buy it like this?

Timing is a static adjustment. You'd have to manually and purposefully change it. Swapping the carbs won't mess with your timing, and it won't unsync you unless for some reason you saw a need to unbolt the linkages or the throttle body.