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Lavey29
04-26-2006, 11:05 AM
I was wondering if anyone on here has tried switching to a 2'' shorter lower unit on their drive. If so, did you pick up a few miles an hour and did you think it was worth the expense?. I have an IMCO drive am considering going with a shorter lower unit to pick up a little more top end. Anyone tried it on a larger size 30' V bottom. I know that it depends on your current drive height and whether or not you already have a high X dimension but just wanted to get some feed back from some people who have tried it and liked or did not like the results. Thanks for the help...

BADBLOWN572
04-26-2006, 11:57 AM
A while back, we tried a 2" shorty on a 28' deep V. We were trying to get more top end out of it. Was not a smart move. Prop started blowing out of the hole, needed to be real gentle on acceleration, and handling became an issue. The only way that we were able to fix the problem was to install a stand off box.
It really depends on the setup of the boat as well as the boat itself. Some boats will run much better with a shorty on it, but on a lot of boats it will negatively effect the handling. I would call Lavey and see what they have on their race boat. That right there would be pretty much the ideal setup. Lots of R&D in that program.

Havasu47
04-26-2006, 12:09 PM
You MUST know your propshaft height in relation to the bottom before you can decide what length lower will help. If putting a 2" shorter lower moves the propshaft to the optimum location, then it will help. It could create a nightmare if it is already at the optimum height.

burtandnancy
04-26-2006, 12:21 PM
As Bad Blown said above, every boat is different and has different characteristics. A lot of care and considerations must be taken...

WYRD
04-26-2006, 12:32 PM
who in their right mind would switch to a 2" shorter lower unit? :idea: :crossx:

Phat Matt
04-26-2006, 12:38 PM
who in their right mind would switch to a 2" shorter lower unit? :idea: :crossx:
What's 2 inches when you have to tuck it in your sock? :crossx:

WYRD
04-26-2006, 01:12 PM
What's 2 inches when you have to tuck it in your sock? :crossx:
you must wear stockings then :crossx:

Phat Matt
04-26-2006, 01:31 PM
you must wear stockings then :crossx:
Nah, the little booties. :p

Lavey29
04-26-2006, 01:36 PM
A while back, we tried a 2" shorty on a 28' deep V. We were trying to get more top end out of it. Was not a smart move. Prop started blowing out of the hole, needed to be real gentle on acceleration, and handling became an issue. The only way that we were able to fix the problem was to install a stand off box.
It really depends on the setup of the boat as well as the boat itself. Some boats will run much better with a shorty on it, but on a lot of boats it will negatively effect the handling. I would call Lavey and see what they have on their race boat. That right there would be pretty much the ideal setup. Lots of R&D in that program.
Thanks for the info. I did talk with Kevin down at Lavey and he said it might help with top end as long at when I tried to get on plane now there was no prop blow out. He said that I could probably shorten the drive and still have decent planing time while picking up a few miles an hour and that if I was having problems getting out of the hole then just instal a drive spacer. Similar to what you did but just not going with a full extension box. I wish they had a demo program and if it worked then you would by the unit. Thanks again for the info,,,take care...

Lavey29
04-26-2006, 01:45 PM
You MUST know your propshaft height in relation to the bottom before you can decide what length lower will help. If putting a 2" shorter lower moves the propshaft to the optimum location, then it will help. It could create a nightmare if it is already at the optimum height.
I agree with you. What is the best way to know if you are already at the optimum height location. My boat has no problems planing now with the tabs down but I do not slam it from the start. I just roll it onto plane so as not to stress the drive with to much torque. I know that a shorter unit will decrease your trim levels for your boat but I do not require much positive trim with the Lavey so that shouldn't be a problem.

Tom Brown
04-26-2006, 01:46 PM
I would call Lavey and see what they have on their race boat. That right there would be pretty much the ideal setup. Lots of R&D in that program.
That right there is gold. :cool:
BTW, the blow out problem of a raised engine can often be solved/mitigated with different prop choices. IOW, the best prop will vary with your setup.

BADBLOWN572
04-26-2006, 02:07 PM
Thanks for the info. I did talk with Kevin down at Lavey and he said it might help with top end as long at when I tried to get on plane now there was no prop blow out. He said that I could probably shorten the drive and still have decent planing time while picking up a few miles an hour and that if I was having problems getting out of the hole then just instal a drive spacer. Similar to what you did but just not going with a full extension box. I wish they had a demo program and if it worked then you would by the unit. Thanks again for the info,,,take care...
If you go with 2" you will see a drastic difference in the way the boat accelerates and handles. Normally 1" makes a big difference 2" will make the boat a completely different animal.

Lavey29
04-26-2006, 02:12 PM
If you go with 2" you will see a drastic difference in the way the boat accelerates and handles. Normally 1" makes a big difference 2" will make the boat a completely different animal.
So it sounds like you don't recommend it or after you got yours dialed in with the box and everything do you think it was worth the money and time?

BADBLOWN572
04-26-2006, 03:02 PM
So it sounds like you don't recommend it or after you got yours dialed in with the box and everything do you think it was worth the money and time?
It is a big gamble! Luckily I did not pay for the ones that I did. It was for a customer. When it was all said and done, I want to say that he picked up 1-2mph and spent roughly 3500-4k for it.
My guess is that your height is pretty close to where it is ideal at. I do think that 2" will be too agressive of a move. 1" would be as big as I would go. But, that is jut my .02

cdog
04-26-2006, 03:07 PM
I need to go to a 3 inch shorty. Mabey you'd be intrested in my IMCO 2 inch short? It's in perfect condition and only has 1 season on it. PM me.

Lavey29
04-26-2006, 04:04 PM
It is a big gamble! Luckily I did not pay for the ones that I did. It was for a customer. When it was all said and done, I want to say that he picked up 1-2mph and spent roughly 3500-4k for it.
My guess is that your height is pretty close to where it is ideal at. I do think that 2" will be too agressive of a move. 1" would be as big as I would go. But, that is jut my .02
Thanks for the good advice pal,,,4k for 2mph doesn't quite fall within my burger and fries budget