Help Donzi Pulls to the right!

[Trebor]

Hello to every one.

I'm the proud owner of a 1970 18' 2+3 Donzi Holly and Moody edition. The boat has a new engine 351 Windsor and the original Volvo pinta 250 out drive. The prop has been changed to a stainless 21 pitch not sure of the make, but its on heavy duty prop. The boat has been clocked at 74mph on GPS.

The boat will run at 45mph straight as an arrow. Can let the wheel go. But as the boat goes faster it pulls to the right. This pull increases at the the speed increases. It seems to put a lot of strain on the boat (And me). Can any one give me some hints on this problem?

:propeller

[McGary911]

Sounds like you have a boat with the steering on the left, and a LH turning Volvo, which is typical. The tendancy to veer right is from the torque of the prop tilting the boat to the right, which induces a right turn. There are a few things you can do to minimize this. Some props are much more likley to exaggerate this tendancy than others. Do a search under props and you'll find some good info. Make sure your torque tab, a little skeg behind your prop is canted slightly clockwise, which is to minimize the torque steer. Finally, if you have tabs, you can drag a little right tab, just enough so when the hull starts to lean right, it lands on the tab, and will stabilize. This scrubbs a little speed, but if you already have tabs, you can try it next time out. I'm sure more good (assuming this was good :) ) advise will follow.

[David Ochs]

Welcome to the Registry.
My boat acts the same way. Unfortunatly the 250 only has fixed trim, so you're forced to select a position that suits you the best. For my boat (same set up as yours), having the outdrive trim full down seems to work the best.
Play with the skeg adjustment to help compensate for "torque steer".
I think everyone would agree that adding trim tabs, power trim, and hydrualic steering would be ideal. But without all that, make a compromise and find the settings that generally work the best.
Good luck

[boldts]

Trebor - sounds like a simple fix by moving the exhaust outlet tab that sticks down from the drive plate right behind the propeller. Yours may have been changed to a smaller, less cumbersom torque tab since your getting 70 + gps. Thats doing some serious speed for an older 18 Classic. BTW, its Holman and Moody (http://www.holmanmoody.com). They used to build NASCAR engines for the Ford boys and special race cars like GT40s. First before changing the tab position, set your drive trim where you want to run the boat most of the time. This effects how the tab works also.

Anyway, you will have this torque at some speed all the way up to wide open. There is an allen wrench screw on top of the plate. Loosen it and I believe you move the tab in the direction that your steering wheel is trying to turn. Go in little increments and notice the change it makes to your steering torque. If it gets worse, I'm wrong and you need to go back to where it was and then a little more the other way. Been a while since I played with one of these. Here is where you need to decide how you want to run the boat. You can set this tab so that steering is 1 finger at wide open speed or if most of your cruising on the water is done in the 60mph range, move the tab so that you have 1 finger steering in that speed range. What will happen is you will have more torque on the steering wheel at wide open, but the boat will be comfortable in your normal use speed. If you run the boat wide open everywhere you go, then obviously set the tab for 1 finger at WOT.

The other option is look around on the Internet for stories about guys who have adapted a hydraulic steering system to the older Volvo drives. It was very expensive back when I had mine so I never got into it, but there are guys who have done it. Anyway, once you go hydraulic, it will be like driving your power steering truck. No more torque at any speed.

One last thing, if you have pictures you can post, I know I personally would love to see your Donzi. It sounds assume!

[Trebor]

Thanks to every one! This is a great site.

I think the problem lies with the boat not even having the skeg. Seem like its an important item to have. Can any one let me know good place to get a skeg for my outdrive? Are there different size skegs, and will this effect HP?

The boat has no trim tabs. I have seen them on the newer 18' Donzi's. I will defiantly be looking into this to add on the boat.

The trim is in a whole other category. Completely new for me. It seem that the out drive is to be in a looked position. But the boat has a power trim. There are three locking position. Right now set to the middle. But once the outdrive is locked the trim will not work. Is there a reason for this? And how are you to unlock the outdrive and trim up when pulling the boat out of the water? I have been jumping in the water to unlock and trim up.

Its going to be a nice weekend in Barrie Ontario. Hope to get some great shots of the boat this weekend.

[David Ochs]

Trebor,
Don't confuse trim with tilt. These old outdrives don't have power trim, only power tilt. When you tilt the outdrive up, the plunger presses against a small bullet shaped pin that releases the reverse lock and will allow the drive to tilt up. The mechanism is simple yet tricky to repair if not working properly. You might want to see what's going on with it, having to jump in the water at the ramp would get old with me.
Years ago I bought an inexpensive book published by "Seloc" by Joan and Clarence Coles that covers all this stuff. Although not an official Volvo manual it has a lot of info for cheap$.

[boldts]

Are you sure you have the Volvo 250 outdrive? Those didn't come with power trim. Only the 3 hole trim setting that the trim bar goes thru to the other side. Unless, and this is something I looked into also, someone came up with a way to add power trim to your drive. Again, I had people who said they could do it for an astronomical price tag.

With that said, you should have a trailer tilt switch on the dash that works to lift the drive for trailering. This is an electrical plunger that is on the inside transom to the right of the engine as you look backwards from the back bench. Mine would never hold the drive up when you hit the throttle. In fact, thats usually how I knew I forgot to put the drive all the way down again. It can however be used at an idle if your in shallow water to lift the drive up and still move the boat.

As for the skeg, contact a member named BigGrizzly here on the boards. He is the one who told me about the smaller slimmer torque tab. It was said to help the speed a bit because it wasn't so big and bulgy like the exhaust tab.

The more you tell us, the more I'd like to see your set-up through pictures. Sounds like someone put a lot of work into your 250.

[Danny]

Trebor
We are in Midland, do you boat on Simcoe? Wouldn't mind seeing your boat some time.
My 16 handled very similar to what you described, we upgraded to a volvo 280 with trim and tilt, put tabs on the boat and now in the process of doing the external hydraulic steering.
Send me an email sometime. We are off to the wooden boat show in Gravenhurst this weekend.
Danny

[Danny]

Sorry forgot this part
Volvo parts sales and service
Jim Langley Marine in Honey Harbour.
(705)756-1662
He has been a volvo dealer for over 30 years. He has worked on a variety of old Donzis with volvos, knows his stuff and nice guy to deal with.
The book DavidO mentioned is a very good investment.
Danny

[mattyboy]

what kind of prop are you running??? all the stated above can be causes too but the wrong prop will also cause it , My 250 with a spinelli on it was a real work out at any speed no matter what i did with trim settings and torque tab settings it still did it, threw a chopper on it and did it but not has bad and now with the ultra I get NO torque steer at all

good luck post pics

[MOP]

If you still have th original exhaust relief tab you need to get rid of the it, they do squat for trimming the steering and some feel they steal speed. You will get some effect changing to a fin stlye tab, do search we have a member that has made them up to fit your drive I forgot WHO!

Phil

[David Ochs]

If you still have th original exhaust relief tab you need to get rid of the it, they do squat for trimming the steering and some feel they steal speed. You will get some effect changing to a fin stlye tab, do search we have a member that has made them up to fit your drive I forgot WHO!

Phil

I've been searching and had no luck. If anyone finds the source for the "fin style tab" that Phil mentions, please post it.
Maybe with one of these I could get my wife to drive the boat. Is that a good thing?

[olredalert]

-------Middle hole of the three is widely recognized as the best position for all around performance. Bottom hole keeps too much hull wet for good speed and top hole will, more often than not, airyate (SP) the prop. Matty is right about different props being better or worse. Its a trade off a lot of the time. You have to figure out what speed you run at the most. I know Im getting old when I say this but I dont prop a boat for top speed anymore. I prop for good upper cruising speed at an RPM that the engine or engines seem to like to run, and just let the top end take care of itself............Bill S

[MOP]

The tab pictured in the lower shot of the link below is the one I am talking about, drop Lenny a note I think he has one and he does know who makes them.

Phil

http://www.donzi.net/forums/showthread.php?t=37797

[David Ochs]

The tab pictured in the lower shot of the link below is the one I am talking about, drop Lenny a note I think he has one and he does know who makes them.

Phil

http://www.donzi.net/forums/showthread.php?t=37797


Thanks Phil

[JimG]

On my 1970 18 I have no torque fin. When running my old aluminum props, torque steer was a BIG problem. Under hard acceleration, the wheel would almost rip out of your hands. Switched to an Ultra, and no more torque steer.

On the third hole, the torque steer was back. Fast, though. Switched it back to the second hole, and torque steer was gone.

[YoAnthony]

JimG,

My 1971 GT21 351HM 250 Volvo has an aluminum prop. Any reccomendations on an ultra and where do you sorce them?

I've only had the boat out once to see if everything worked and did not notice torque steer. It has no adjusting fin on the outdrive, the hole has a plug in it.

Thanks,

[JimG]

I bought mine off of EBay. Then had an inch of pitch added. I know the guy who has the Ultra molds, maybe he could be convinced to make a few if there was interest.