What is happening with my motor???

[dennisopie]

My Mercruiser 470 idles fine, revs fine and goes into gears but when I took it to the lake and it would only get to about 2.5k rpms and it would start to cut out and almost die. After it had almost stalled out and the rpms got lower it would sometime back fire a little. When not in gear the engine will hold rpms much higher. If I didn't give it more throttle it would run fine but as soon as you gave it more gas and went over 2 to 2.5 rpms in gear it would start to stall. Carb issue? It just had new points put on it.

Here's my boat if you want to take a look. There is a video of it running at the end.

1985 Four Winns Horizon 190 For Sale in Spring, TX - YouTube

Not for sale anymore

 

[achris]

Re: What is happening with my motor???

Standard troubleshooting for an engine.

I'm going to suggest what I suggest to everybody with these sorts of problems... I've had my hand bitten off a few times because people think I'm calling them an idiot... I'm not, it's just a very good, solid, sound troubleshooting method.... If you don't like what I say, don't be rude about it....

Engines require certain things to operate properly... Basically they need the correct fuel/air mixture to be compressed and then fired at the right time.

So, in this order.

1. Compression tests.
2. Check spark plugs, replace if needed.
3. If points, replace, along with condenser and rotor. Check and adjust, if needed, points cam dwell angle.
4. Inspect distributor cap and leads, replace if necessary.
5. Check spark quality (needs to be a nice BLUE spark drawn over 1/2").
6. Set timing. Check timing advance is working correctly.

When all of these items have been done, THEN move to the fuel system....

You can have the best, cleanest carburettor in the world, but if the compression's low and/or the ignition system's not doing its job, the engine will still run like crap.....

Chris.........

 

[thumpar]

Re: What is happening with my motor???

That is a good checklist. Also the fact that it will rev without load doesn't mean anything.