Atomic 4 won't rev under forward load

[rayncyn51]

I appreciate all of your input. I have learned much about the nuances of the A-4 powertrain. Feedback from the Catalina 30 forum and Moyer Marine also cite fouled prop or fuel starvation as primary culprits. The first thing that I am checking is the prop. Prior to this use, the boat had not moved from her slip in the Chesapeake in almost 4 weeks. Come to think of it, the bottom was a lot greener looking that it had been! We will be on the boat again this weekend. Will let you know what we find. - r

Dog, TY, Point taken and understood. I have read here and elsewhere of marina electrical issues. As a relative novice, I'm really surprized that this piece of info isn't more widely published in boating safety kinds of literature. go figure...

[timebandit]

Take a fuel filter with you just in case.

[jakemo86]

I've been having a very similar problem with my 72 A4 but my problem doesn't arise till i have been in gear for quite a while no less than 1.5 hours and it just seem to bog down and eventually kills the engine completely, but when i kick it into neutral it runs fine and as long as i let it sit for 10-15 min it works fine for a while more. I've already gone under to check for any fouling or debris on the prop or shaft and found nothing at all the oil has just been changed and I intend to change the fuel filter as soon as i get a replacement and get it loose. The fuel filter appears to be pretty old so im hoping thats the problem although it doesn't make complete sence to me it almost seems like its over heating but i don't know how.

[Valiente]

That could be a partially occluded tank vent (like with spider webs). The tank can't vent properly and eventually overcomes the mechanical fuel pump and the carb is starved. Because it's only a partial blockage, tank pressure equalizes under little load. Dissemble the gas tank vent and blow it out. If crap comes out, that's the likely answer. Switch to a larger diameter hose (I use 5/8" ID) and get a fine mesh vent screen.

If it doesn't, change the fuel/water separator or fuel filter. You should do this anyway.

Lastly, crud in the tank itself can gradually occlude the pick-up tube. Same deal to fix that...

[rayncyn51]

And the winner is… Fouled prop! And bottom, big time!

We had the boat pulled on Thursday morning and found at least an inch of barnacles and other Chesapeake Bay marine habitat growing on the bottom. The bottom was clean in March when she was splashed. The yard guys were amazed that the boat had only been in the water that long and had so much stuff growing on her.

Supposedly, the PO had the bottom done last season. Either there is a huge difference in anti-fouling requirements in the Chesapeake than there is in North Carolina where I bought the boat, or the PO used the equivalent of swimming pool paint instead of anti-fouling!

Anyway, we cleaned up the bottom, put her back in the water, and she runs great! Thanks again to all for your input.

Ray'n'Cyn
Lady Kel-e, C-30 #1455

[Valiente]

Good to hear it. The A4 is a simple beast, but being simple, it is easy to blame for things not necessarily its fault. Some TLC and a bit of knowledge will keep it running for years in the typical sailboat regimen of "motor out, head to weather, sails up, engine off....repeat in reverse coming back". A low-compression gas engine (properly ventilated with a blower, of course) is a better choice by far for the typical sailor who uses the engine for only short periods. A diesel is best left on, once on, at a cruising RPM for hours, such as a motorsailer would do.

You might want to delve into local lore regarding prop treatments and bottom paints in your area. The brackish conditions seem to be very challenging in the Chessie, from what I can gather, and it may be that the best solution is simply a weekly scrape.

[timebandit]

I would replace the ign coil--that is how they go.

Originally Posted by jakemo86

I've been having a very similar problem with my 72 A4 but my problem doesn't arise till i have been in gear for quite a while no less than 1.5 hours and it just seem to bog down and eventually kills the engine completely, but when i kick it into neutral it runs fine and as long as i let it sit for 10-15 min it works fine for a while more. I've already gone under to check for any fouling or debris on the prop or shaft and found nothing at all the oil has just been changed and I intend to change the fuel filter as soon as i get a replacement and get it loose. The fuel filter appears to be pretty old so im hoping thats the problem although it doesn't make complete sence to me it almost seems like its over heating but i don't know how.