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boat steering pulling to the left

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tmcboat

Regular Contributor
Hi All,
My boat steering is pulling to the left- constantly having to put pressure on the steering wheel turing it to the right.
I have a left hand rotation prop on a Volvo penta 270 on a 27 ft cruiser.
Which way to I turn the exhaust snout to get the steering neutral pulling? do I turn the rear of the exhaust snout to right or left?
thanks,
tmcboat
 
I installed a no feedback helm last year and it cured the issue do you have a rotary helm or a rack and pinion? I didnt have the room for a rotary so I had to go with a teleflex rack.
 
Ya got me there-- there is a cable under the steering wheel that goes back to the rod that pulls and pushes the round yoke- thats all I know but I heard you can adjust which way the boat is turning by moving the exhaust snout fin right or left-- I just need to find out if the boat is pulling to the left which way do I point the rear of the exhaust snout fin
thank
tmcboat
 
Tip..... when talking about boats, try to use the terms; Fore, Aft, Port and Starboard. No mistakes nor misunderstandings that way! ;)



tmcboat said:
Hi All,
My boat steering is pulling to the left- constantly having to put pressure on the steering wheel turing it to the right.
That would be to the Port side!

I have a left hand rotation prop on a Volvo penta 270 on a 27 ft cruiser.
Which way to I turn the exhaust snout to get the steering neutral pulling?
Since the "steer torque" is taking you towards Port...... you will "counter" the steer torque by tweaking the trim fin/torque tab also to Port.
The problem is....... the exhaust outlet housing for the 270 drive is lousing at this!

And by the way...... you will be able to correct this within a certain speed range only.
It will not correct steer torque at all speeds.
So make your correction for the speed that best keeps the boat up on step comfortably.


By the way #2 ...... no-feed-back steering systems simply mask the helmsman from feeling the steer torque..... it's still there, and it's tugging away at your mechanical components causing unnecessary and pre-mature wear!

Point being.... even with a No-Feed-Back system, we still want to properly adjust the trim fin/torque tab best we can!
Click to expand...
 
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Hi Rick and All,
thanks for the info-- we will adjust the rear of the exhaust stout to port-left- and adjust for cruise rpm and speed for about 26 to 29mph cruise. The fin on the 290 is 3x the size of the 270 unit. Why couldn't I bolt a hydrofoil fin on that makes the 270 fin larger like the 290 fin-- ? does the hydrofoil fin slow the boat down or load the lower unit gears and bearings.It seem that the 290 would do the same? your thoughts please
thanks,
tmcboat
 
............................
tmcboat said:
Hi Rick and All,
thanks for the info-- we will adjust the rear of the exhaust stout to port-left- and adjust for cruise rpm and speed for about 26 to 29mph cruise.

The fin on the 290 is 3x the size of the 270 unit. Why couldn't I bolt a hydrofoil fin on that makes the 270 fin larger like the 290 fin-- ?
A "hydrofoil" adds horizontal surface that helps to create stern lift.
The "trim fin/torque tab" (vertical plane) is there to counter "steer torque" only.


270 and 275 style drive exhaust outlet housing and it's rather ineffective trim fin/torque tab.
https://encrypted-tbn3.gstatic.com/...lIoHjFmApik_Aal30sLPYTJpbyELakiyRvTMQCMhUtBp0

280, 285, 290 drive exhaust outlet and a seperate and more effective trim fin/torque tab.
(look closely....... you can just barely see the trim fin/torque tab)
https://encrypted-tbn1.gstatic.com/...KZ3rWcf65aPVKBD8nZfsZEtbpYWP2fQuHAPj5-cx8h3zA
Click to expand...
 
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HI Rick and all,
you are right about the 270 exhaust fin/ torque tab -poor control on solving steering issue. I will look into getting a used 290 lower unit to bolt on-- advantage--more blade surface area with long hub prop, better stern lift, larger exhaust ports? better steering.
thanks,
tmcboat
 
.............................

tmcboat said:
HI Rick and all,
you are right about the 270 trim fin/ torque tab - poor control on solving steering issue.

I will look into getting a used 290 lower unit to bolt on--
This is not exactly a "bolt-on" affair. You must perform the critical bearing race shimming when changing lower gear units.
It is fairly easy to do....... you just need to educate yourself on the procedure!
Since you have a 27 footer, you likely have V-8 power so you'll need the 1.61:1 lower gear unit.


advantage--more blade surface area with long hub prop,
Yes!

better stern lift, larger exhaust ports?
Plus...... it will be less restrictive because you can eliminate the exhaust back-flow-prevention flapper that may be within the exhaust bellows!

better steering.
Yes, because the trim fin/torque tab is more effective.
Click to expand...
 
re: "better stern lift, larger exhaust ports?
Plus...... it will be less restrictive because you can eliminate the exhaust back-flow-prevention flapper that may be within the exhaust bellows!"

In the final analysis, the small hole(s) thru the transom shield are the major cause of back flow issues, not the flappers. They do not meet the generally published port sizes for V8s...especially the 350 cid ones. Single port size for this class engine is specified as 4 inch diameter. The total area of the holes ( 2 on the pre 280 drives, 3 on the 280 and later drives) do not add up to anywhere near the area of a single 4" dia ( or dual 3") hole. The size of the "wide" port on the 280/290 is irrelevant for flow purposes since, much like the flow restristor washers on your showers at home, the thru holes at the transom are the limiting factor.

I've measured over 6 psi of back pressure on a 350 CID engine on a 250 drive.... waaaay over factory specified 2 psi for 350 class engines. But what the hey, so long as the engine lasts longer than the warranty period, what does the factory care.
 
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