Too fast

[smp]

Hi all,

my boat moves too quickly in idle, what can I do about this? I'm not sure what the prop specs are, I think I have a pic somewhere of the prop from when it was out of the water and the numbers that were on it. I'll see if I can find that but I'm fairly confident that the prop is original to the boat.

The way that i deal with this is by putting the boat into neutral, coasting along, putting it into forward gear for a few seconds and back to neutral. This is when I'm docking and manouvering in tight quarters. I can not coast in idle inside a marina, the boat moves too quickly.

Question: should I get another prop?

Or

Is what I'm doing ok?

The gear shift lever is loose and sloppy, and neutral is very difficult to get just right. The prop is typically spinning one way or the other (albeit very slowly) when I have the boat in neutral. I will open the locker and look at the shaft and tap the lever until I get it stopped. This doesn't seem normal.

[Dave Neptune]

Perhaps

Steve, the prop may help however slowing the idle may do more.
What is you idle speed in RPM's? If you show over 800 at idle it should be able to be slowed down. I idle at around 800 and in gear it's about 700 idling in forward.

Dave Neptune

[Bold Rascal]

What a great problem!

If your idle is any where near where it should be and it still travels too fast I'd like to know what kind of prop your running.

[smp]

Without a tach, how do I monitor my idle? It _sounds_ like it's idling where it should be. And I say that not because I know what an A4 sounds like at 800rpm but I monkey around with bikes and cars and like to think I could hear a high idle .. then again, I don't know for sure.

[sastanley]

steve,

this all sounds like normal operation to me. It is typical for A-4 boats to be slightly overpropped, and with a direct drive you are spinning the prop at the same speed as the motor. These two problems combine to = too fast at idle.

Changing props would help, and getting the idle speed as low as possible would help too.

Your procedure to coast and come in and out of gear is normal too. I don't worry too much about a slow spin on the prop when 'coasting'. if it is spinning 1 or 2 revolutions per second (60-120 RPM), it is not really doing anything to help push the boat...in fact, the prop could be spinning while you are coasting from the water passing over it while in neutral.

I put this problem as one of the disadvantages of a direct drive arrangement. A reduction drive of 2:1 drops your prop speed in half, and would likely help slow idle speed too.

My 10x7.4 3-blade prop moves the boat slower than my 12x7 2-blade did for sure at idle...I sometimes still have to coast.

[Dave Neptune]

Try slowing her

Steve, do you know someone with a tach/dwell meter? If so you could use it to set the idle speed.

Comparing engine sounds at idle is OK however these old 4 banger flatheads really sound slow at a base idle of around 600.

Try backing out the idle speed screw a bit and see what happens, you can always speed her back up if necessary.

Note once the boat is at any speed reducing the throttle to idle will take a long time to slow if in gear. What is your idle speed in forward? My 35 takes a long time to slow from cruise if I just drop back to idle, she slows much much faster out of gear!!

Dave Neptune

[yeahjohn]

In forward with minimal current or wind I run at about 3 knts at 850rpm. I think most of us use neutral and reverse often while docking and maneuvering in tight areas.

[Sony2000]

Disconnect your throttle at the carb. Back off the idle screw beside the area at the end of the cable wire. Your idle speed of the engine will drop. Drop it to an RPM that will let you put the engine in gear, and not stall. Reattach the throttle, to hold that position. This must be done before you think of changing props.

[sastanley]

I definitely agree with Sony that your initial focus should be on any adjustments available to you above the waterline, to get them 'right', before doing something drastic like changing props.

That is the most logical approach.