1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

Hi all,

I just got a 1969 Thunderbird Shawnee that came with a Merc 1000. I've taken the boat out on the water but I can't seem to get it to speed up as if the boat is too heavy. Then it started to die when I put it in gear.

It was in the garage all winter. The few things I did before getting out on the water were:

1. Changed the spark plugs
2. Replaced the fuel line
3. Removed the prop and checked all
4. Opened the merControl and looked over the cables and wiring.

A few items that are interesting is that there are 2 levers on the merControl. One is for the idle and one is for the throttle. The engine will rev really high with the idle lever but again when put in gear is simply dies. I also smell a lot of gas and will only start when using the choke even if it's already warmed up.

Here are a couple of pics. Thanks for viewing and helping out.

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

I made some modifications to the carbs. Reset the air/gas mix and adjusted to about one and a half turns out. Also tightened the spark advance. I realized that it died because the spark adv was moving to far back and killing the engine. However; it still dies when put in gear and there is a lot of oil in the testing tank.

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

right now my symptoms sound the same on a different mariner motor, and i believe i am getting a bypass of air into the fuel mixture. i have a new diaphragm coming for the pump but have not installed yet so i don't know if thats the cure. however, my fuel primer ball hardly stays hard.

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

Jeff Lindquist said:

right now my symptoms sound the same on a different mariner motor, and i believe i am getting a bypass of air into the fuel mixture. i have a new diaphragm coming for the pump but have not installed yet so i don't know if thats the cure. however, my fuel primer ball hardly stays hard.

Click to expand...

I realized that the the primer ball does get a bit soft and I also see bubbles in the in-line fuel filter. My problem might also be at the tank. At first I was not sure if I was mixing the gas correctly but I'm mixing 50:1.

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

that sounds like the correct mixture. my diaphragm is in so will do that and rebuild the fuel line and primer bulb as well then tank test tonite. i'll let you know what i find. if i knew someone with an extra tank, i'd like to swap out and compare as well. i'll advise results

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

How is the compression?

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

If the compression is good, I would pull the carbs apart, my guess is a blockage in the carb jets or fuel pick up. Strip it down, give it a good soak, flush all the galleries with an air compressor. Set the idle jet at 1.5 turns out from lightly seated. (This is more likely if the boat has been sitting a while) (do consider that I am not a mechanic but this has worked for me)

Re: 1969 Merc 1000 -100 HP - Starts, idles, runs but dies when put in gear.

reinstalled fuel pump last night and rebuilt fuel line from tank with ne ball and clamps. tank test went well and i had to lower the idle due to high revs. seems to be fine on land but still have to lake test. i was getting extra air in the mix somewhere along the line for sure.