Hello,

we are having problems with a brand new (5hrs runtime) 700sci. The engine is litterally one week old.

when putting it into gear it can run for 5-10 seconds and then stall. Both when in reverse or forward.

we are running #6 drives with 18”x26p cleavers. So very big propellers.

we have around 5-6 feet of exhaust with gibson mufflers on the end that is half submerged under the waterline. So we can expect a bit of back pressure here.

the thing is that the stbd engine with 15hrs runtime does’nt stall.it works fine every time.

we have installed bam gearboxes that required some modifications to get the correct amount of wire play from the levers. Could this have something to do with the neutral micro-switch not in sync causing the engine to stall?

someone told me that there is an air bypass screw that can be adjusted near the iac module?

thanks for any input or help!! Boat is delivered to customer and we need to fix this asap!

Have you hooked the engine up to a scanner, or better yet, a laptop with Diacom??? That would be step #1.

Post a few pictures of the installation, cable hookups, shift linkage

So we have checked the tps and iac controller. Everything works like it should.

same boost pressure and fuel pressure as the other engine.

after yesterdays test-drive we saw that the engine the stalls uses 9.5 gallons per hour more than the other.

it seems like the problem is a brand new #6 drive.

we have tested with other props and same problem. 9.5 gallons is the same as 114hp.

anybody had this problem with a #6 drive before? It is straight out of the box. 15hrs on it, no racing, no jumps etc…

Does the drive spin freely by hand or is it dragging binding

Swap the drive and see if the problem follows....could be in the trans too I suppose but seems like it would do it all the time unless there's something dragging in there in gear?

Does it do it on land too or just in the water?

Can you bypass the shifter so you can start the boat while in gear? When it stalls out in gear, and if kept in gear, your starter should have a hard time rotating everything
Edit:
Probably won't work because engine needs to be running to be in gear

Check for misfire/bad coil. The engine has idle rpm control and sometimes it can be hard to hear a consistent misfire. With a big pitch / gear ratio, it is hard to maintain idle without all cylinders firing. Fuel consumption and top speed could be affected too.
You can also disconnect the interrupt switch on the intermediate shift bracket. It is the one in the middle of the bracket that a ball detent moves a plunger against. It isn't "necessary", but it does help with high load shift out of gear, a problem with the trans, and also Bravo clutches, that wear the internal brass bump rings a lot so I don't recommend it as a long term fix/test. It has a preset timeout in the interrupt if held on, but it may be too long to avoid stalling. It is an easy thing to try.

Not sure what you have for a boat but if it's staggered there is also the drive shaft support housing at the transom that could be bad and is seizing up. Sometime people forget about those and that they have to be serviced. That would add strain to the drive line.