constant boat drift from side to side

[pocoloco]

Not sure if I am posting in the correct forum but...<br />here's the question:<br />I have a maxum 1998 1900Sr (19ft bowrider) with a 4.3L mercruiser engine (190 HP). at slow speed up to speed on plane the boat drifts left, then right, then left, then right and it does this in a fairly extreme way, making manouverability difficult. When on plane the boat keeps steady. <br />I thought it may be the power steering, slack somewhere in the system, but when watching the power steering cylinder I noticed no movement while the boat drifted from side to side.<br />My current suspicion now lies with perhaps prop choice? I only just got thre boat and it has a 4 blade SS prop with 24 pitch. Could an inapropiate prop cause the boat to wonder?<br />any tips would greatly help.

 

[QC]

Re: constant boat drift from side to side

Probably should be a boat topic, but I'll help you. Totally normal . . . common problem with planing v-hulls. You learn to anticipate and make smaller corrections. Also, trim tabs in a full down position help a lot. Good luck.

 

[rodbolt]

Re: constant boat drift from side to side

what quietcat says. its common and a lot of times if you make no corrections it will swing back. if you correct make small ones and give it time to change.

 

[pocoloco]

Re: constant boat drift from side to side

Hm, I can't imagine it being normal this extreme although I know that its normal for boats wonder a little... why do v-hulls wander sidewards?

 

[rodbolt]

Re: constant boat drift from side to side

its called bow steer. sometimes you can use the trim or reposition some weight to help off set it. <br /> if you have the prop clearence switch back to the anode that looks like a fin and see if that will help.

 

[bomar76]

Re: constant boat drift from side to side

It's normal.<br />Fixes?<br />Trim tabs down all the way helps a little.<br />Not overcorrecting all the time helps more.<br /><br />Best fix?<br />Buy a twin.

 

[Richard Petersen]

Re: constant boat drift from side to side

I have a Chapp that does the EXACT same thing. I am sure it is because the lower case does not have enough vertical area. NO RUDDER, so they can go faster. Who wants to steer easily when docking in a wind or current.----------------- I did see a small guy in the drive flipping it back and forth.

 

[Richard Petersen]

Re: constant boat drift from side to side

My 16' Alum. fishing boat goes straight in a hurricane. It has a LOT of the lower unit as a rudder. About 6" boat bottom to prop.

 

[trog100]

Re: constant boat drift from side to side

having the drive trimmed all the way down improves mine.. its still a pain thow.. just more of a pain with the drive up slightly..<br /><br />i do a lot of low speed river and canal cruising.. so it matters more to me than most.. i have to tolerate it most of the time..<br /><br />its not that bad it makes manouvering in confined spaces difficult.. it just needs constant attention and hands on the wheel all the time with lots of small (in advance) corrections.. and at really low docking speeds the slightest breeze blows the boat any way but which way..<br /><br />i think its just with a shalllow v hull wideish beam relative to lenght boat thats how it is.. not much of a keel.. no rudder.. in essence there is nothing to keep the boat going straight at low speeds.. a bit like an arrow with no flights..<br /><br />trying to steer vaguely in the right direction (nothing to line up the pointy bit with) to a gps or compass heading is even more of a pain.. he he..<br /><br />my sons 20ft boat has a narrower beam.. more of keel and is not quite such a shallow v as mine.. it tracks perfectly straight at low speeds.. it dosnt handle as well at planing speeds thow..<br /><br />trog

 

[KaGee]

Re: constant boat drift from side to side

Look up "Smart Tabs" in the boating, Non-engine forum.

 

[QC]

Re: constant boat drift from side to side

It's the hull not the rudder. I/Os are HUGE rudders, and the propulsion is directional.

 

[Richard Petersen]

Re: constant boat drift from side to side

I/O's are not huge rudders. All of it is blocked by the deep V hull. And in many stock boats the top of the prop is within 1" of the hull bottom. A deep V hull is one big straight keel with strakes, lots of straight lines there, to keep the boat straight. Deep V inboards do not wander at all compared to the I/O's.

 

[trog100]

Re: constant boat drift from side to side

the boat is steered by the off-set thrust of the prop.. the actual drive itself dosnt act like much of a rudder at low speeds.. if it did i would be able to steer my boat when its on the kicker by turning the wheel and useing the outdrive as a rudder.. i cant so it isnt much of a rudder..<br /><br />at higher speeds when the prop is shifting lots of water past the bottom of the outdrive.. skeg and trim fin it does keep the boat steering straight but at low speeds there really isnt much to keep a shallow V keel-less I/O from wandering.. so its not surprizing it does..<br /><br />the bit i cant really explain to myself is how it self corrects a lot of the time when u just let it wander.. praps its just random.. a wander to the left followed by a wander to the right.. dunno..<br /><br />trog

 

[Richard Petersen]

Re: constant boat drift from side to side

That is the part no one has come up with the right answer for. It self corrects in any wind or current, from any direction. WHY? We are stuck with it for the most part.---------------------- Better built boats. WHERE?

 

[QC]

Re: constant boat drift from side to side

Originally posted by cyclops2:<br /> I/O's are not huge rudders. All of it is blocked by the deep V hull.

Measure the surface area of your inboard rudder and the surface area below the ventilation plate on an I/O. Most if not all of that surface area is below the hull. I cannot explain why trog cannot steer his boat when on the kicker. My boat steers well when it is out of gear and still moving. I have 20 degrees of deadrise.

 

[Richard Petersen]

Re: constant boat drift from side to side

I have had it on this " Duck walking " by Mercruiser I/O's. Monday, tech support meets me on the cause and cure of it. --

 

[trog100]

Re: constant boat drift from side to side

quitecat.. just for interest.. my I/O dosnt steer at all in neutral.. it makes for some dicey moments having to come in to dead end moorings or concrete locks at 4 mph and relying on a quick blast of reverse at the last moment.. he he..<br /><br />u have me wondering now.. yours steers in neutral mine dosnt.. ??<br /><br />i wonder which is the more common.. ??<br /><br />mine really does rely on offset prop thrust to steer..<br /><br />also the guy i bought my boat off.. had the kicker fitted with throttle and gear change at the helm.. the guy who fitted it said the boat would steer with the wheel.. ??.. it quite clearly dosnt.. not in the slightest..<br /><br />its now a two man operation useing my kicker.. someone up front to work the gears and throttle and another bugger at the back to steer the boat with a 3 foot extension handle.. i would be better without all the extras.. he he he..<br /><br />trog

 

[Richard Petersen]

Re: constant boat drift from side to side

Agreed Trog. I had a 16' fish boat with a 9.9 and a 28 hp coupled with a steering bar. The 9.9 on power was terrible. The 28 was better. Took the 28 off. Love the 9.9 by itself.

 

[pocoloco]

Re: constant boat drift from side to side

thanks for all those comments, it seems as though everyone has the same problem... I somehow still wonder whether the propeller pitch has an influence on the intensity of the sidewards drift. My side drift is in my opinion extreme (+/- 30 degrees maybe). No one mentioned prop characteristics, so i gather the prop has nothing to do with this... I run the trim at lowest position, have no trim tabs.<br />curious to know how cyclops2 tech advice goes.

 

[trog100]

Re: constant boat drift from side to side

just one last thing.. my sidewards drift would probably be as bad as 30 degrees without the constant corrections i put in without even thinking about it..<br /><br />at first it was more like 45 degrees with my poorly applied "over-corrections".. he he he..<br /><br />i think smart tabs would help.. but then again dragging a log behind me on a rope probably would.. a shallow v planing boat is pretty much like a kite without a tail at low speeds in my opinion..<br /><br />trog