Help, mercruiser wont rev
 

Took my 1985 formula 242 to the bahamas. Boat has twin 5.7 260 hp mercruisers with carborators . Came across ran great no issues. Tyed to the dock and the Boat sat for 2 days in the water in pouring rain, now the port engine won't idle in gear, won't free rev over 2000-2500.. starboard engine runs fine. I have replaced the fuel filter, checked the plugs, and swapped the coil. I haven't checked the cap and rotor because one of the screws broke off in the cap and I'd like to not destroy the cap if it's not the issue, getting parts here is about impossible. I'm hoping someone has an idea of what else I can check. I'm on a small island and have no fuel pressure gauge and no timing light. If I can't get it sorted out, my option is to fly home come back with a complete ignition system, box and dist and coil and prayers.

Have a hair dryer or fan ? Blow in the 90* fitting on the distributor cap. Becareful with non shielded electrics in bilge. Make sure totally free of fuel vapor.

If you have non of the above, open the hatch and position the boat so that sunlight can shine on the whole engine, especially the distributor. Or , maybe you should do this first. Dry breeze and warm sun can do wonders.

Might want to check the ign wire boots on the cap to see if water got in the cap terminals....Don't break a ign wire. Doh.

Also, if your bilge wasn't fast enough, check the power wires at the starter. All the power connects to the battery here also.

Good luck ! I'd be crapping myself too....but remember......keep a cool head so you can thin.

Broke the screw out of the cap and swapped the dist and ignition boxes side to side, looks like a bad dist pickup or bad ign box, can't isolate further all the connections are diffrent . Have a local who has a boat in his yard that he's gonna pull the box and dist out of and see what happens

Cool deal. Hope someon e has a timing gun. Hope it all works out.

Remember, many bad situations turn into a great story later on.

"Remember that tripo we took in the boat to.....and......" LOL

Hope you got this fixed to get home, how did you make out?

Well what a weekend, ended up finding a drill and drilling the head off the rusted screw. Pulled the cap and was able to swap the boxes side to side. Found the boxes were ok on both engines. Swapped the distributors side to side and found one would not run on either engine. Bad pickup sensor in the distributor, I actually found a guy with a complete distributor out of a dead boat, and bought it. Installed it and had a similar issue.. No way I have another bad pickup. Swapped coil, nope, swapped ignition boxes, nope swapped cap and rotor nope. So still have a bad distributor. Booked a flight to ft lauderdale, called west marine the one in north palm beach had one, rented a car, and drove to palm beach got the sensor and a timing light ( and picked up a part for anther stranded boater) and flew back. Put the sensor in and fired it up, ran great to 2500 rpm.... Wtf... Played around, now my ignition box won't run over 2500 on either engine. Tried to drive the boat on one engine, not a chance, she will do 5.5 mph with one engine, not a chance of a plane. If I could have gotten 10 mph I would have driven it home. I gave up and hitchhiked a ride home. I have 2 ignition boxes and a distributor out of a running boat and a new xap rotor and coil. Fly back Saturday to get the boat. Fun with boats.

Flew back last weekend 7am sat got the boat running. Had breakfast at big game fueled up and headed out at 11. Had totally flat water for the first half of the trip and was running about 50. About mid way had some little chop didn't slow me down .. Back under the bridge at 12:10. Boat ran great no issues, and now I have a spare ignition system.

What was it ?

I wish I could tell you. The full story is I plugged a new ign box in and it ran perfect. Set timing revved it up it was mint. I got breakfast drank a kalik. Went back to the boat tossed the lines and put it in gear and wouldn't rev over 1200. I was pretty upset, tied it up, pulled the distrubutor, and dropped in the the other complete ignition systemì from my bag. Complete distrubutor, box, coil cap and rotor fired up set timing it was mint. Tossed my line and hauled a... Figured as long as I got it on plane I could make it home, but it ran fine the whole way. I shut off at the dock here and started it back up, it was still fine. I'm leaning towards it was something in the distrubutor pick up but who knows. None of it makes sense. But the boats home.

I would buy 2 new dui setups. They work great and use GM parts so they are available anywhere.