1978 Mercury 800 Stalling When Shifting

[sje0123]

I have a 1978 Mercury 800. It runs great once the boat gets moving. The problem comes from shifting from Neutral into Forward. Reverse seems just fine and never stalls.

Currently, I have the idle set a little high (800-900rpm) hoping that would help w/ the issue as if I give a little rev on the controls while shifting into gear it goes fine. Recommended RPM is 550-650 at idle. I'm just worried w/ revving I am putting added stress on the gearing. I also raised the idle because when the controls were set to neutral it would die at idle.

Now, when I bought this there was old gas in the tank. Very small amount so it wasn't worth me draining it. I'd imagine it's probably all run out by now but perhaps that's one issue? After running it for about an hour yesterday I shut down so we could hang out a little and relax. When I started it back up it no longer stalled when shifting. However, pulling into the ramp it stalled.

Where do I start with finding the issue? The carbs (according to PO) were rebuilt recently. How recently? I don't know. As well as it runs I can't imagine that's the issue.

 

[starkyb]

Re: 1978 Mercury 800 Stalling When Shifting

If the tank was fairly empty it could have moisture in the tank. You can put fresh gas in but if there is moisture in there it will seem like there are other problems. Im not saying this is the case but it is something you can resolve with a full tank of fresh gas and a bottle of Heet. It made a huge difference in my motor. Unfortunately I went through everything in my motor before I tried that.

 

[sje0123]

Re: 1978 Mercury 800 Stalling When Shifting

Good suggestion. I'll give that a go. I can't confirm how long the tank sat but I know it could have been 2 yrs. So that def could be the case.

I'm trying not to dig deep into it before going over simple things. I've done that too many times just to realize it was something very simple and a lot cheaper.:facepalm:

 

[starkyb]

Re: 1978 Mercury 800 Stalling When Shifting

Tell me about it. I had problems for two seasons so I rebuilt all three carbs, changed the plugs, decarbed the engine replaced fuel lines and paid somebody 85 bucks an hour to go through pretty much everything just for him to tell me I had water in my tank. He discovered this by hooking my motor to his tank and it ran great when he did. It has run beautifully since I did the full tank with Heet. Let me know if that helps.

 

[Texasmark]

Re: 1978 Mercury 800 Stalling When Shifting

Orrr if all that is ok, my serv manual says 675 in F gear in idle. That rpm lets you shift and keep the engine alive yet not bang your drive train...Too high an idle rpm will do that.

Mark

 

[sje0123]

Re: 1978 Mercury 800 Stalling When Shifting

And that's what I'm worried about. Pretty much same things as doing neutral drops on an automatic transmission. That's why I want to get this resolved.

From what I have also read my issue may also be the air/fuel mix @ the carbs. I'll have to stick it in the water one day and just keep adjusting everything like the manual says and see if I can get it running better. I'll try the Heet as well.

This is an old Starcraft SS that's been neglected the past couple of years. I've got a bit to do to get it perfect, but I'm almost there.

 

[sje0123]

Re: 1978 Mercury 800 Stalling When Shifting

And I'm guessing you used the Heet in the red bottle? Seems the yellow bottle is no go for 2cycle.