78 Mercruiser 4.0(I think...?) Straight 6 Running Rough

[Tball94]

Alright, so my dad and I have been tinkering with my boat for the last few weeks, so far what we've replaced (because we thought that these things were causing issues, which some were) are points, condenser, coil, and I've rebuilt the carb, fuel filter.

It runs just fine at idle, which makes me think everything should be okay, then when you give it some throttle it falls flat on it's face.

Things I've done for troubleshooting include checking the spark(it has very strong spark, will jump almost an inch and still let the engine run), checked fuel(it has plenty of fuel...)

At this point we are kind of at a loss. Any ideas would be great. The only thing that my dad can figure is that I ordered the wrong points for it and that is causing the issue.

 

[nola mike]

Check compression, timing/dwell, plug wire order, make sure the distributor is advancing?

 

[Tball94]

Yeah I guess there were some things that I forgot to mention that have been done.

The dwell/timing has been set 3 or 4 times now. Plug wire order should be fine, it was running fine last season and the wires haven't been moved since.

What is the best way to make sure the distributor is advancing?

 

[alldodge]

Start with compression, it might just be a weak motor

Can you give it throttle real slow and have the speed pick up?

 

[Tball94]

Giving it throttle at all causes it to fall on its face.

Also, I've had this boat for what will be going on my 3rd year, it ran strong last season. However, I will test the compression tomorrow when I get to working on it. Will report back with findings.

 

[Scott Danforth]

Im guessing if compression is good, the accelerator pump circuit is plugged

 

[nola mike]

If he's light on the throttle, should still be able to get up to speed

 

[Tball94]

Good morning/afternoon all.

Since last night when I posted this, I thought about it some more, went and got a tune up kit from a local marina (spent more than I probably should have, but wanted to get on the water this weekend) and put it in. Fired it up, and it runs perfectly now... It seems that the points and condenser I had originally ordered for it were the wrong ones and getting the right ones fixed all of the issues I was having.

What did I learn from this experience? Make sure the parts you are getting are the right ones when you do it. Thank you all for the suggestions and the help you offered.