40 plus-won't run in the water

[gcw47]

Hello all - My SJPL long shaft starts and runs on 2nd or 3rd pull just fine on the stand, dry, for short periods. Carb squeaky clean, nice fat blue spark, complete fuel system clean-up performed. On my sailboat, RPMs drop and it stalls out as soon as the prop is fully in the water. I'm thinking mixture first. Needle is flush with the top of the slide. It's #3 and 10:1 fuel is fresh. Carb primes normally and engine runs well - until the prop goes under. I searched the forum and could find no posts that described this problem directly. Any ideas are much appreciated in advance. Thanks

[Horsley-Anarak]

Have you measured the compression?

What is the history of this engine, has it stood idle for many years.

H-A

[Jerry In Maine]

how far under the surface is the prop once its lowered?

[gcw47]

I don't have access to a compression tester, but the thumb-in-the spark plug hole test suggests it's good and you can feel good compression when you pull on the rope. I can't detect any leaks around the head gasket. I recently aquired the engine and know nothing of it's history, but it shows signs of being well cared for and I don't think it has been laid up for a long time. I put new rings in it and it's a brand new cylinder. I did reuse the old head gasket.
I lowered the prop to the recommended water depth of just a couple of inches above the exhaust port. The power starts to drop off as soon as the prop gets about half submerged.

[billyboy]

i wouldnt mind betting that you have no back and forward play in the propeller shaft! check that first if there is not a bit of movement in that direction the engine will NEVER run under any load! i discovered this myself only a couple of months ago!

[gcw47]

It has some play - about 1/8 " or so in the propeller shaft. It runs very well with no load, moves lots of water until it dies off.

[billyboy]

hmm..... ok. still sounds like a gearbox problem to me. maybe check the thrust washer....cant think of anything else at the moment

[Hugz]

Doesn't run under load?? Play around with choke to check mixture. Check points and timing. Check lead and use new plug. Doesn't sound too tragic.

Start her in the water with full choke and 3/4 throttle. Might just be cold. Assume it is something simple.

[OwdJockey]

Have you tried running without the prop for a while?

Definately a Seagull prop?

Are yiou testing on boat and or in dustbin? I know obvious stuff.

[gcw47]

Most assuredly a Seagull prop-says 40plus on it. I tried adjusting the choke while it was in hte aeter and dying - didn't make any difference. Have not tried running without prop in the water. This weekend I'll try it off the boat , in a dustbin ( garbage can over here) Doesn't seem likely to be a bottom unit problem. It does have a brand new plug, properly gapped. I haven't checked the points, but I'll do that as well as double check the ignition plate for timing. Thanks.

[Vic]

It has the correct exhaust tube with two pressure relief holes near the top on the back ?

Presumably not a clutch model so do you simply have the idle speed set so low that it'll run in the air but once immersed the load imposed by the prop being in the water stalls it. (Trying it with no prop will tell you if that's the case)

I start mine in the water at about half throttle.

[Collector Inspector]

Cylinder base gasket OK?

Crankcase halves sealed up?

Regards

B

[gcw47]

Found this problem and now this little engine runs well. I did not initially check the points because they were sealed up in the little round box, which I couldn't figure out how to open, plus the majority of the forum posts said if you seem to have good spark, don't mess with it. Turned out the points were at a very loose .020 and the adjusting screw was loose also, allowing movement of the point gap. Tightened up the screw at a good snug .020 tried it in the tank first without prop -good water flow- then put on the prop and it churned up lots of water. It seemed to start and run best with the mixture adjusting screw 1 and 1/4 turn down. From all I have read, this should be OK.
Thanks to all for the replies.