Driving slower with a 350/alpha?

erikgreen

Captain
Joined
Jan 8, 2007
Messages
3,105
Guys -

I drive my 21 foot boat with a 350 engine and pre-alpha drive up on lake superior for purposes of running a side scan sonar (well, most of the time).

This last weekend I found out that one reason I'm getting so-so quality sonar images is that the towfish is too high in the water. With a 200 foot scope it's only about 25 feet down at 4 miles per hour. I can't add more weight or a deflector wing to it, the manufacturer says the cable won't take it. He said I'm driving too fast.

So I have two questions:

1) How will driving at 650 rpm idle for extended periods (3-4 hours at a time) affect my engine? Should I put some sea foam through it each month or something, or is using it this way ok?

2) Can anyone think of a way to go slower with this engine? I've had trolling plates and sea anchors suggested, and the sonar guy said to get a kicker motor or trolling motor.

My speed with a 13 pitch prop is about 4 mph at idle, a bit less into the wind.... and that's too fast :\

Erik
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Driving slower with a 350/alpha?

1) How will driving at 650 rpm idle for extended periods (3-4 hours at a time) affect my engine? Should I put some sea foam through it each month or something, or is using it this way ok?
Howdy,

Running at idle won't hurt a thing as long as your raw water pump is in good serviceable condition, your idle mixture adjustment is correct and the choke is not closed in any way after warm-up.

Sea Foam is really good for people that sell it...They make money..... It's advantages for the people that buy it are suspect.......It's just a naptha/oil product so putting it in your engine has the potential to foul plugs. If I was going to idle for long periods of time I wouldn't put ANY snake oils in my gas or oil. (I wouldn't do it anyway!!)



2) Can anyone think of a way to go slower with this engine? I've had trolling plates and sea anchors suggested, and the sonar guy said to get a kicker motor or trolling motor.
Other than drag devices, lower pitch prop, and lower idle, you don't have many other choices other than a "Kicker " (Which I would consider because it'll will use FAR less gas than running a V-8 for hours)


Cheers,

Rick
 

Bondo

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Staff member
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Apr 17, 2002
Messages
70,469
Re: Driving slower with a 350/alpha?

Running at idle won't hurt a thing as long as your raw water pump is in good serviceable condition, your idle mixture adjustment is correct

Ayuh,... Idling don't hurt a thing,... I troll for Hours 'n Hours at a time...
Although stock carb settings are just alittle Rich...

My 21' starcraft 4.3l, Alpha has a torque-shift prop, so pitch is 11" idling...
I have Oversized Bennett trim tabs(12x18") that I put at Full down,...
I can troll at Sub-1mph,...
If the wind is Really blowing,... I toss out a 60" sea-anchor on each side, tied off to a forward cleat(keeps 'm out of the stern area, fishing ya know)...
Then I can bump it up to 1000rpms for better boat control...and still be at 1mph or so...

Either dirty up the hull, or twin the tow cable so you can fin the unit,...
That's about the only options I see...
 
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