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wandering and hunting

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SYDMAR

New member
Hi all
Got the engine running right and ran into another possible problem. At slow speed (from idle to about 2000 rpm the boat will not track straight. It will wander to starboard and slowly back to port and slowly back starboard, etc. If you try to correct each heading change it just makes it worse and keeps the helmsman real busy! If the wheel is left alone the boat will get to the desired heading with an "S" wake. Any suggestions?
I'm not sure this is the right forum, but none of the others seemed to fit.
Another quick question that does fit this forum. I came across a manifold for my AQ131A. Mine is a single carb, single throat Solex. The one I came across was a two carb manifold. As this boat is being built to troll on lakes the fuel economy is important (troll all day and not worry about refueling). If the dual carb could be set up as a progressive linkage I could troll at low throttle settings using just the one carb and then when it's time to get back to the dock, open it up and run with both carbs. Anybody heard of this or have any thoughts?
Thanks,
Martin
 
IMHO, you should post the wandering in a different part of the forum. As for dual carbs staged linkage, it can't be done. I believe the front card is for the front two cylinders and the rear carb for the rear two. and you won't gain much horsepower as the dual carb was for the larger engine. You might only get 5 more horsepower.http://forums.turbobricks.com/showthread.php?t=24675
 
Thanks Dennis,
As I mentioned, none of the other forums seemed to fit. Got a suggestion? As for the dual manifold - thanks for that info. I wasn't aware it was a split manifold. Tks again, Martin
 
SYDMAR said:
At slow speed (from idle to about 2000 rpm the boat will not track straight. It will wander to starboard and slowly back to port and slowly back starboard, etc. If you try to correct each heading change it just makes it worse and keeps the helmsman real busy! Any suggestions?

If the dual carb could be set up as a progressive linkage I could troll at low throttle settings using just the one carb and then when it's time to get back to the dock, open it up and run with both carbs. Anybody heard of this or have any thoughts?
Click to expand...
Martin, you're sensing typical bow wander with an I/O at low speeds.......... The key is to not over-correct.

As for the twin carburetor intake manifold, to my knowledge these are split, but with an equalizing section between the two pairs of main runners.


At low speed, your engine is going to require X amount of combustible air, and Z amount of atomized fuel.
I'm thinking that whether this comes from a single carburetor, or twin carburetors, the sum of X and Z are going to be very close to one another.



.
 
Thanks again Guys.
I'm thinking maybe now is not the time to complicate things with multiple carbs. My experience with this was with a couple of Corvettes with a 327 and two four barrel carbs set up with progressive linkage. Worked great.
The response to the bow wander seems to be "live with it". I will check for loose parts but the hydraulic or power steering solution is a little pricey! Part of the build on this boat is using Pro-Troller tabs to slow it down. One of the replies to this thread mentioned a sea anchor correcting his wander. I'm hoping that the drag from the Pro Trollers may work the same way?
Speaking of which---I know the Pro Troller tabs (made by Smart Tabs) are relatively new, but has anyone had any experience with them?

Thx, Martin
 
The way I eliminated or minimized low speed steering wandering is by installing hydraulic steering and having a steering helmet with no play. You may also experiment and find another system that works for you.
 
SYDMAR said:
  1. The response to the bow wander seems to be "live with it".

  2. I will check for loose parts

  3. but the hydraulic or power steering solution is a little pricey!

  4. Speaking of which---I know the Pro Troller tabs (made by Smart Tabs) are relatively new, but has anyone had any experience with them?
Click to expand...

  1. In many cases, this is the simplest and least expensive solution.
    Try to not over-correct, and see what happens.

  2. That would certainly help.

  3. Hydraulic would be my preference over that of Power Assist, but it may not completely solve bow wander.
    Part of bow wander is a result of I/O hull characteristics.

  4. Smart Tabs are generally and typically for smaller boats.
    If you need helm controllable trim tabs, these are not the way to go, IMO.
 
Thanks Rick -
The tabs were ordered to slow down the trolling speed without having to resort to a trolling plate or a separate trolling motor hanging off the stern. These tabs stick straight down into the water on each corner of the hull (in trolling mode) and leave the prop wash unobstructed for better steering control. Their hype says they improve the problem of bow wander. They work as normal tabs at speed, control bow lift, quicker plane, etc. (even if you forget to raise them!) The hull I have is an 1852 Bayliner cuddy.
Martin
 
Ok folks,
Installed the ProTabs and ran it today. They eliminated almost all the bow wander and did slow my trolling speed! I'm amazed that something actually lived up to the Hype! When I get a Hummingbird fish finder with the GPS I'll be able to get a better idea of how much it slowed me down. The only complaint with the Tabs is you have hang over the stern and reach down underwater to trip the levers. Now, a couple more questions. How warm should the AQ131A run? At idle and trolling it runs about about 140 degrees. But when I open it up and run at 4500 rpm it jumps up to about 200 degree. Is this normal or is this a little hot?
And the last question: I'm topping out at 4500 rpm. Should I not ge topping out around 5000 rpm? If this is correct I should be able to run either a smaller diameter prop or a little less pitch? This would let me troll even slower without fear of over reving at the top end.
Thanks, Martin
 
Martin, 180º-198ºF is the temperature range of the thermostat. You are doing fine.

It you want to top at 5000 RPM, make sure first that the throttle cable is properly adjusted, that the carb flame arrestor is not dirty, that the engine is properly tuned-up and that the tachometer is working fine. Also, make sure the boat does not carry too much weight and that the hull is not waterlogged. If all the above is fine, then you may need a prop with about 2" less pitch than the one you have now, which will probably bring your maximum RPM to about 5000. Mind you, I don't think you will want to run the engine continuously at those RPM.
 
Thanks for the info, el_pescador!
The temp readings are good news. The throttle cable is adjusted correctly, flame arrestor is clean, I do hear a tappet clicking slightly, and the boat is empty other than me. The waterlogged hull is a question. I hope it isn't! What is a reasonable RPM for continuous running?
Thanks again, Martin.
 
SYDMAR said:
What is a reasonable RPM for continuous running?
Click to expand...
Like Eduardo said...... do not operate continuously at 5k rpm, or you will shorten the life of your engine.

See your OEM specified WOT RPM range, and prop the drive accordingly, and with the boat loaded as you would normally operate it.

Your cruise RPM will be determined by what is required to get the hull on top of the water, plus some.
Hopefully, this will be well below the 5k rpm.

There are only two efficient speeds.

Hull speed and below.... and planing attitude and a tad more.
Anything between these may over-burden your engine, and it will most definitely waste fuel.


.
 
SYDMAR said:
Thanks for the info, el_pescador!
The temp readings are good news. The throttle cable is adjusted correctly, flame arrestor is clean, I do hear a tappet clicking slightly, and the boat is empty other than me. The waterlogged hull is a question. I hope it isn't! What is a reasonable RPM for continuous running?
Thanks again, Martin.
Click to expand...

Martin, the first thing you should do is to read your Engine Operator's Manual. If you don't have one you can download it from here:

http://vppneuapps.volvo.com/ww/PIE/...403&d=Owners Publication&s=3965887&lang=en-GB

According to VP, your engine maximum RPM range is 4700-5000, and the recommended maximum cruising speed is 300-500 RPM below the maximum. From that perspective, your current prop should be OK (4500 RPM is pretty close to 4700 RPM). When it comes to decide at what RPM to operate an engine, I personally try to determine at what RPM range does the boat achieve its best fuel consumption and seem to run happy. For that, you will need a fuel flow meter and a GPS. The flow meter does not have to be an expensive one; in fact any of the cheaper units will do, because once you have determined the best RPM via experimentation, you just cruise at those RPM. If you want to go that way, you may want to invest around 150 bucks in a cheap flow meter like this one

http://www.bethel-marine.com/NavMan_F2100.htm

then install it in your boat, and use your GPS (or borrow one) to find the fuel consumption and speed at different engine RPM. You can then plot on a chart (or just use a spreadsheet) the values engine RPM, fuel consumption and gps speed. Then you calculate the fuel consumption per nautical mile for each RPM at which you took spped and fuel consumption readings and you will find at which RPM range your engine burns the least amount of fuel. To determine the fuel consumption per nautical mile (or land mile if you prefer) just measure with the GPS the speed in miles per hour and write down the fuel consumption in liters (or quarts or gallons or whatever unit you prefer), then divide the liters/hour by the miles/hour and you will obtain liters/mile. It's a worthwhile exercise that will help you save quite a bit of $$$ over time.
 
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Thanks guys,
The RPM range you gave is helpful. If I read el_pescador's response correctly, 2 inches of pitch equals about 500 RPM (?). I'm not really looking for max RPM as much as slow (trolling) speed without risking someone else over revving the engine while pursuing non-fishing activities. Thanks again! Martin
 
SYDMAR said:
Thanks guys,
The RPM range you gave is helpful. If I read el_pescador's response correctly, 2 inches of pitch equals about 500 RPM (?). I'm not really looking for max RPM as much as slow (trolling) speed without risking someone else over revving the engine while pursuing non-fishing activities. Thanks again! Martin
Click to expand...

As a rule of thumb, a 2" decrease in propeller pitch will increase your engine maximum speed in 300-400 RPM.
 
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