Fast Turns With A I/O

[AJ163]

Guys, a question regarding handling at speed..........

I've just upgraded from a 17 foot with a 115 Hp outboard to a 19 foot Monterey bowrider with the 5.0 I/O. During the test with the dealer he advised me not to power through turns with the new boat as it would place a lot of pressure on the ...gimbal??? Some part where the engine connects thru the transom. He added that it wouldn't cope with turns as well as my outboard boat.

At the time I was at about 3000 revs and doing a lazy u-turn to head back to the marina. His comment did make me think to myself that surely the boat is designed to conduct high-speed turns (not like jet boat turns) and can be powered through turns providing you aren't literally spinning through your wake.

Surely most people whilst caring about their boat, enjoy powering it through turns, etc. What's the opinions within the forum?

Thanks

AJ

 

[dave11]

Re: Fast Turns With A I/O

I looked at a 26 ft Doral with a big engine and an I/O and a Duoprop. I did the same thing on the Manatee River on a calm smooth day. The guy said "don't turn it so hard." Well, I spend most of my time in the Gulf. It gets pretty ratty out there pretty quickly sometimes. I can't imagine what would happen if I had to crank it around in heavy weather. I gave him the helm and told him "We're done". I wanted a seaworthy boat, not a floating raft.

That was the first and last I/O I expect I will ever drive. I have always had outboards, and I guess that is what I'll stay with.

 

[slasmith1]

Re: Fast Turns With A I/O

I wouldn't rip it all the way over to the stop at WOT but tight turns at 3000 rpm have never caused a problem. I have been boating my whole life with I/O boats and have only owned one outboard that wasn't on a dinghy. So do with my advice what you will.

EDIT: just feel your way through if it starts to cavitate back out of the throttle a little or straighten the wheel a little.

 

[AJ163]

Re: Fast Turns With A I/O

Yep..practically same comment I got dave, its the duoprop I have as well.
I've got the same attitude as you, Slasmith, don't intend to trash the boat, but at same time want to have some fun with it.

I've been trying to recall exactly what else the dealer said that day, he also commented something about the drive not acting the same as an outboard drive would, if applying power when the boat is cranked over in a turn.

Part of me wonders if it is because this dealer tends to sell 30 foot plus boats rather than runabouts. Anyone else make sense of what he's basing his comments on?

 

[livin4real]

Re: Fast Turns With A I/O

Guys, a question regarding handling at speed..........

I've just upgraded from a 17 foot with a 115 Hp outboard to a 19 foot Monterey bowrider with the 5.0 I/O. During the test with the dealer he advised me not to power through turns with the new boat as it would place a lot of pressure on the ...gimbal??? Some part where the engine connects thru the transom. He added that it wouldn't cope with turns as well as my outboard boat.

At the time I was at about 3000 revs and doing a lazy u-turn to head back to the marina. His comment did make me think to myself that surely the boat is designed to conduct high-speed turns (not like jet boat turns) and can be powered through turns providing you aren't literally spinning through your wake.

Surely most people whilst caring about their boat, enjoy powering it through turns, etc. What's the opinions within the forum?

Thanks

AJ

I'm assuming he said it puts pressure on the Gimbal Bearing. The driveshaft of the outdrive slides through a big bearing in the Gimbal Housing and into the engine. When the wheel is cranked all the way the bend of the u-joints puts added pressure on the gimbal bearing so adding excess power to it exacerbates the issue BUT I have never been one to shy away from sharp turns at power with any of our boats (all I/O), especially if my kid comes off their skis or tube in the middle of a busy lake. I'm sure it's not the greatest thing for them but I have never noticed any excess wear because of it. Quality bearings should have no problem lasting as long as the bellows provided they are kept lubed and dry.

 

[Texasmark]

Re: Fast Turns With A I/O

Mercruiser, know not of others. An I/O has one more drive shaft angle than an outboard to go through since the engine is mounted horizontally rather than vertically sitting on the drive shaft as is the case with outboards. In getting through that 90 degree angle they use a "gimbal" which is a pair of bearings horizontal and vertical, both with support (a pair of roller bearings) on only one side of the gear.

Preceding the horiz shaft/bearings/gear is a "constant velocity joint" whose job it is to allow the outdrive to turn, yet have the drive shaft from the engine in a fixed position.

Lateral (sideways) forces on that joint increase drastically as the turn angle is increased. This can cause noticeable vibration and is annoying on systems with some wear and transoms that are not adequately supported (alum boat). BTDT

If you ever drove a farm tractor with a pull type rotary (Brush Hog is a brand) mower behind it, listening to the drive line rattle in turns is exactly what I am talking about. Only difference in the boat is that the upper and lower u-joints are combined in one assembly (constant velocity joint) for convenience and the fact that the distance is short. I had a rear wheel drive automobile once that had a CV in the driveline, and most front wheel drive cars have cv's.

Knowing what I know about them, I too would take it easy in hard turns, but that's my opinion.

Mark

 

[Subliminal]

Re: Fast Turns With A I/O

So how is this different than making a turn at speed in your Honda Civic?

 

[Aviator5]

Re: Fast Turns With A I/O

CV joints and U-joints are 2 big differences

 

[AJ163]

Re: Fast Turns With A I/O

Thanks guys...have learned quite a bit in a few posts!!! As an ex-farm boy, understand exactly what was meant reference the driveshafts and joints. And though never turned that hard with PTO shafts fitted, on occasion had to whip tractor and machinery round quick on occasions and never did any harm - but understand the potential from having had a few drive shafts crack and seen the resulting mess......and cost!

Probability is that only time I'll be doing hard turns is in same situation as Livin4real - when somebody comes off the board or tube.

Thanks all

AJ

 

[Subliminal]

Re: Fast Turns With A I/O

CV joints and U-joints are 2 big differences

From the previous post I was led to believe that both use CV Joints, rather than universal.

 

[QC]

Re: Fast Turns With A I/O

This is an operations question so I'll leave it here. We would typically have the technical portion of this discussion in the I/O section . . .

Steering on an Alpha has a total travel of 56 degrees (28 degrees from straight) while trim is only 15. With that noted, the concern regarding full power above trim angle is that the gimbal support flanges are out of play. With any u-joints the concern is always the angle of deflection, so it makes sense that high power, hard over turns are working the u-joints pretty hard. However . . . there is not one mention of power application and steering angle in the Mercruiser manuals. At least I don't recall one and I kinda read through them often . . . There is, however, a very complete discussion about power levels (RPM) and exceeding trim angle. It is possible that the lack of warning about steering angle has to do with liability though. Who would want to recommend not turning as far as possible when necessary . . .

How's that for muddying the water?

 

[Subliminal]

Re: Fast Turns With A I/O

That's a strange looking joint. So, it really isn't a CV joint, but rather two u-joints in close proximity..?

 

[livin4real]

Re: Fast Turns With A I/O

This is an operations question so I'll leave it here. We would typically have the technical portion of this discussion in the I/O section . . .

Steering on an Alpha has a total travel of 56 degrees (28 degrees from straight) while trim is only 15. With that noted, the concern regarding full power above trim angle is that the gimbal support flanges are out of play. With any u-joints the concern is always the angle of deflection, so it makes sense that high power, hard over turns are working the u-joints pretty hard. However . . . there is not one mention of power application and steering angle in the Mercruiser manuals. At least I don't recall one and I kinda read through them often . . . There is, however, a very complete discussion about power levels (RPM) and exceeding trim angle. It is possible that the lack of warning about steering angle has to do with liability though. Who would want to recommend not turning as far as possible when necessary . . .

How's that for muddying the water?

Clear as mud? (as my old shop teacher used to ask me)

And what I failed to elaborate on the whole "quality bearings should last as long as the bellows" statement is that the bearing should be changed whenever bellows are replaced since it's tore down already. The last set of bellows I changed, the gimbal bearing looked great from the outdrive side looking in, but once I pulled it, it was pitted and rusted on the inner side. Spend the extra few dollars and replace the bearing while in there.

 

[nlain]

Re: Fast Turns With A I/O

That's a strange looking joint. So, it really isn't a CV joint, but rather two u-joints in close proximity..?

That really is a CV joint, I saw it years ago, 1960's and 70's, in automotive drivelines and it was called a CV joint, it just is not the same CV joint that you see today.

 

[rjlipscomb]

Re: Fast Turns With A I/O

When the dealer demonstrated my boat (done by the service dept manager) he noted to use caution and low power while the drive is tilted up. He demonstrated the boat while making sharp u-turns and quick s-turns at a fair amount of throttle. The only caution that I remember was to be careful to not turn back into your own wake or something like that. I trust that this man knows what he's talking about.

 

[sickwilly]

Re: Fast Turns With A I/O

I guess I will be replacing mine then, as I whip my little Stingray around when pulling tubes, as well as when picking up skiers. Sometimes a little more throttle at the perfect time in the turn really get the boat a turning.

 

[Philster]

Re: Fast Turns With A I/O

"Should" and "Shouldn't" are subjective things, and they need a precursor to be completely helpful.

It is not very informative to tell someone, "You shouldn't hammer the throttle from 0% to 100% throttle."

What is more appropriate is this: If you don't want your outdrive to need a rebuild every 200 hours, you should avoid going from 0-100% throttle in 1 second".

That type of statement is informative. That statement allows the buyer to weigh the options. Believe me, there are thousands of guys that gladly bury the throttle and accept the added cost of maintenance/repair associated with it. If they had to drive like wusses, they'd not enjoy boating.

I think the same goes for advice regarding hard/fast turns, and all other sorts of boating operations and care.

You can decide on whether you should or shouldn't be doing something, if you have all the information (know the consequences vs. benefits). I know guys that don't care to hear, "You shouldn't leave your boat uncovered." Know what? They know that to cover/uncover their boat would make the experience miserable, so they decide not to do it.

 

[37pro]

Re: Fast Turns With A I/O

From my understanding of this on a merc drive you can wear the steering arm to gimble ring connection. As with anything mechanical "babying" it will make it last longer.
Two u-joints close together are not the same as a constant velocity joint. A u-joint spinning at an angle speeds up and slows down as it goes through the motion. A cv joint does not hence the name constant velocity. Puting two u-joints together like that is the same a very short drive shaft, and as in all drive shafts the u-joints have to be in "phase" or the speeding up and slowing down will result in a bad vibration and breakage. The u-joints are phased to reduce not eleminate the vibration. The bad news is the greater the angle the u-joint is operated at the worse this becomes.
Drive the boat and don't worry about it but keeping an eye on the steering shaft to gimble ring is a good idea "keep it tight". Good luck, Eric

 

[QC]

Re: Fast Turns With A I/O

"Should" and "Shouldn't" are subjective things

Agree

What is more appropriate is this: If you don't want your outdrive to need a rebuild every 200 hours, you should avoid going from 0-100% throttle in 1 second".

I would suggest that this is also somewhat subjective though as the 200 hours is arbitrary and there is a huge difference between a 140 against an Alpha, a 300 Mag against an Alpha and a 320 against a Bravo 1 . . . There is no question that a guy with a blown 350 against an Alpha needs to limit the rate of travel of his right arm . . .

I do agree on the gimbal ring wear and that is more painful than u-joints!!!

 

[AJ163]

Re: Fast Turns With A I/O

QC ...."This is an operations question so I'll leave it here. We would typically have the technical portion of this discussion in the I/O section . . ."

I did consider posting in the engine section, but figured whilst it is related, it's more to do with use of the boat as a whole.

Am very pleased with the responses guys as I've picked up a lot that can be stored away for future reference.

And Philster has summed it up nicely, it sucks when you get told should or shouldn't do something without the whole context being explained. After all the responses, she's going on the water tomorrow for some nice fast sweeping turns as the forecast is good and the engine is just reaching the 5 hour run in point and I can use some revs!!!