No rpm increase after half throttle

[Mahoneymik]

Hi all,
I just watched the Moyer Marine DVD on ignition, and have a couple questions.
It seems like my A4 doesn't reach max RPMs at full throttle. The RPMs stop increasing at about half throttle. The throttle lever goes all the way, but the engine seems max'd out halfway. I don't have a working rpm gauge, so I can't tell you what it's running at. But it seems very low. And it's very low power.
Something I noticed in the DVD was that my wiring harness and the one in the video are connected completely differently. In the video, he says the firing order is 1243. On my engine if I use the same distributor cap numbering, my cylinders go 2431. Is that possible? Could my engine run like that? And could that be my problem?
Thanks for any help!
Michael.

[JOHN COOKSON]

Hi all,
I just watched the Moyer Marine DVD on ignition, and have a couple questions.
It seems like my A4 doesn't reach max RPMs at full throttle. The RPMs stop increasing at about half throttle. The throttle lever goes all the way, but the engine seems max'd out halfway. I don't have a working rpm gauge, so I can't tell you what it's running at. But it seems very low. And it's very low power.
Something I noticed in the DVD was that my wiring harness and the one in the video are connected completely differently. In the video, he says the firing order is 1243. On my engine if I use the same distributor cap numbering, my cylinders go 2431. Is that possible? Could my engine run like that? And could that be my problem?
Thanks for any help!
Michael.

If you read 2431 as 1243 you will see that the firing order is correct. Remember the rotor goes in a circle. Your distributor is rotated 90* from "normal". If the spark occures at #1 spark plug when #1 piston is at TDC compression and the rest of the spark plug wiring is in the correct firing order you're good to go.

Lack of power can have many causes. Dirty\fouled prop, trany adjustment, not enough fuel to the cylinders, timing or ignition problems, stuck valves, exhaust blockage, and what ever else I didn't think of.
Do you notice any symptoms such as missing, backfiring, engine revving but the boat going no faster or what. A video would be helpful. And please, get yourself a hand held or bulkhead mounted tachometer so we can drill down into this.

TRUE GRIT

[joe_db]

A4s being overpropped and thus RPM limited are fairly common. Also easily caused by barnacles on the prop.

[Mahoneymik]

Thank you John

If you read 2431 as 1243 you will see that the firing order is correct. Remember the rotor goes in a circle. Your distributor is rotated 90* from "normal". If the spark occures at #1 spark plug when #1 piston is at TDC compression and the rest of the spark plug wiring is in the correct firing order you're good to go.

Lack of power can have many causes. Dirty\fouled prop, trany adjustment, not enough fuel to the cylinders, timing or ignition problems, stuck valves, exhaust blockage, and what ever else I didn't think of.
Do you notice any symptoms such as missing, backfiring, engine revving but the boat going no faster or what. A video would be helpful. And please, get yourself a hand held or bulkhead mounted tachometer so we can drill down into this.

TRUE GRIT

When I got the boat about 18 months ago, I remember it having much more "pick up" when I hit the throttle. It actually surprised me that a sailboat would move like that. Then all of a sudden, it stopped performing like that. Now it's sluggish at best. I'm gonna try to check the timing and ignition this weekend.
I clean the bottom twice a month, so I doubt it's a dirty prop.
I'll get a handheld tach and try to get a video. Won't be able to until the weekend though. I really appreciate the help.
Thanks!
Michael.

[roadnsky]

Michael-
Just clarifying something...
When you're revving the engine, is it IN gear or neutral?
(Be cautious revving the A4 while in neutral too much)

[Mahoneymik]

Michael-
Just clarifying something...
When you're revving the engine, is it IN gear or neutral?
(Be cautious revving the A4 while in neutral too much)

I notice it most in gear. I don't rev it all the way up in neutral, but I guess I should see if it happens then too.
It's exactly like flooring the gas pedal in your car, and having it only accelerate until your foot is halfway down. The pedal continues, but no change in RPMs or speed. It seems that the engine should rev higher and produce more power, but it doesn't.

[JOHN COOKSON]

When I got the boat about 18 months ago, I remember it having much more "pick up" when I hit the throttle. It actually surprised me that a sailboat would move like that. Then all of a sudden, it stopped performing like that. Now it's sluggish at best. I'm gonna try to check the timing and ignition this weekend. Michael.

Michael
You're on the right tack with your observation.
A4s are noted for their "explosive" accerlation both in gear and out of gear.
If your A4 perfomance has deteriorated it will most likely continue to do so and not get better over time.

TRUE GRIT

[Marian Claire]

When I got the boat about 18 months ago, I remember it having much more "pick up" when I hit the throttle. It actually surprised me that a sailboat would move like that. Then all of a sudden, it stopped performing like that. Now it's sluggish at best. I'm gonna try to check the timing and ignition this weekend.
I clean the bottom twice a month, so I doubt it's a dirty prop.
I'll get a handheld tach and try to get a video. Won't be able to until the weekend though. I really appreciate the help.
Thanks!
Michael.

Could you give more info on "all of a sudden"? Like one weekend she ran great but on my next trip, 2 weeks later, she was sluggish. Or I was cruising along and bam the RPM dropped and she would not rev past 1/2 throttle. Did you make any adjustments or maintenance between running well and sluggish? Do you have the adjustable main jet? Have you watched the throttle linkage at the carb as you push the lever forward? Have you tried partially engaging the choke as she is running?
Dan S/V Marian Claire

[Mahoneymik]

Update:

I had a friend look at the engine last weekend, and he took out the spark plugs and saw that one was full of grime and others were relatively clean as though they were firing properly. He said it looked like my timing was off and had me run the engine while he turned the distributor. As soon as we did that, the engine started running much better and has ever since. He also had me buy some new plug wires. Moyers wires are much beefier than the (crap) I had before. I bought a new electronic ignition but haven't installed it yet.
I just wanted to let the others online here that are having that same problem that mine was solved with just a slight turn of the distributor and some new spark plug wires!

[JOHN COOKSON]

You're on the right track: Get the engine running correctly before making any changes.

TRUE GRIT