IMCO Xtreme Advantage lower unit

[Conquistador_del_mar]

I just got in an IMCO regular length lower unit for my Bravo One drive from a man selling it on Ebay. I was surprised to find that it is not as perfect in the casting as I would have expected, so I spent some time today air filing the case followed by fine sanding and then polishing it with 3M super duty and then 3M no swirl compounds. I think it will look and perform well for my application since I had set my X dimension as high as possible when I changed over to a Bravo drive. Has anyone else been disappointed with their IMCO Xtreme casting or is it just me? Bill

[Ed Donnelly]

Wow; I really like shiney things. :cool: .Ed

[mjw930]

That's purdy :D

The IMCO lowers come in 3 finishes, Black, Polished and Satin. Many like the satin because they claim it has less surface tension. I don't know if I buy into that.

It's likely you got the satin and turned it into the polished version ;)

[SilverBack]

That looks very nice!!! I have the satin lower like MJW said they are supposed to give you a little more top end. Who knows...Sounds kind of fishy to me to??? I understand the principle but who knows maybe a mph at most I would think.

I might have to polish mine up after seeing yours. They say with the satin you have to spray it down with WD-40 and go over it with Scot bright after every outing.

Good luck.

BTW I think LRT and BGZX both run them...maybe they will chime in!

[The Hedgehog]

I can definately see the casting imperfections in mine. I am sticking with the WD 40 and scotchbrite.

That sure is pretty though.

[CJmike]

Shiny. I like it.

[BlownCrewCab]

After the first outing it's going to look like the satin one. I Have had polished, it looks great on the trailer, but after a long day in salt water it didn't shine at all. I Have never tried it in fresh water.

[MOP]

That's purdy :D

The IMCO lowers come in 3 finishes, Black, Polished and Satin. Many like the satin because they claim it has less surface tension. I don't know if I buy into that.

It's likely you got the satin and turned it into the polished version ;)

You should buy into that, it is long proven! Look at any major race boat you will not see any polished drives, they want every last ounce of speed. You must break the stiction layer for maximum performance. This is true even when it come to cylinder head ports, shiny ports costs HP and way more then you think!!!

Phil

[mjw930]

You should buy into that, it is long proven! Look at any major race boat you will not see any polished drives, they want every last ounce of speed. You must break the stiction layer for maximum performance. This is true even when it come to cylinder head ports, shiny ports costs HP and way more then you think!!!

Phil

Of course at 100+ I'm sure it makes a difference, on our boats, I'm not so sure it's measureable.

As for engine ports, I agree 100%. The old "ported and polished" comments give me a good laugh.

[Conquistador_del_mar]

I can definately see the casting imperfections in mine. I am sticking with the WD 40 and scotchbrite.

That sure is pretty though.

Big Green,
I used to install nose cones as part of my services. I never ran across a Merc drive with such ripples in their castings. My customers were always pleased with the finished installation which was always painted black. It really showed any imperfections, so I would spend a fair amount of time to make the contours as perfect as possible. Have you thought about taking out the casting ripples? I might be wrong, but my thoughts are that the ripples would slow the unit down with some suction points. I found that an air file was the easiest way. You could always sand blast it to bring back the satin finish. Bill


After the first outing it's going to look like the satin one. I Have had polished, it looks great on the trailer, but after a long day in salt water it didn't shine at all. I Have never tried it in fresh water.

BCC,
Although I boat in fresh water, I agree that keeping my unit polished would take some effort. I might end up clear coating it or just let it take on the satin look over time. Bill


You should buy into that, it is long proven! Look at any major race boat you will not see any polished drives, they want every last ounce of speed. You must break the stiction layer for maximum performance. This is true even when it come to cylinder head ports, shiny ports costs HP and way more then you think!!!

Phil

Phil,
I have read that over the years and I'm sure there is some validity in it, especially in the extreme speedboats. I had a customer years ago who paid me to sandblast the bottom running pad area of his georgeous boat. Upon followup, he gained no extra speed, however. My guess is that it only really comes into play in a marginal way. Bill


That looks very nice!!! I have the satin lower like MJW said they are supposed to give you a little more top end. Who knows...Sounds kind of fishy to me to??? I understand the principle but who knows maybe a mph at most I would think.

I might have to polish mine up after seeing yours. They say with the satin you have to spray it down with WD-40 and go over it with Scot bright after every outing.

Good luck.

BTW I think LRT and BGZX both run them...maybe they will chime in!

Stang,
My boat presently runs right at 100MPH with a gloss black standard Bravo lower unit with a nose cone installed (by me). I honestly don't think this drive will add any speed, but I am going to install it since it should have more longevity with the higher HP since it has better internal parts. My guess is that a satin finish vs a gloss finish is negligable at these speeds. I am sure someone has performed precision tests on the difference. Maybe they can help validate the difference. Bill

[The Hedgehog]

That is a good thought on the casting ripples. I will look into that.


What kind of setup are you running? That is hauling

[Conquistador_del_mar]

That is a good thought on the casting ripples. I will look into that.


What kind of setup are you running? That is hauling

Big Green,
I have a 1985 23' Eliminator Daytona with a 468CID BBC blower motor probably making only about 600HP with 7.5 lbs of boost. I had to design a custom made 1/2" aluminum plate which I attached with SS button head bolts through the transom to accomodate the new Bravo drive assembly from the previous Volvo Penta which would not take the HP. I set the drive with the maximum X dimension to still get the boat on plane. It is set at about 3" higher than the maximum Mercruiser states is the highest after talking to some speed experts in Florida about 10 years ago. Here is a picture taken a while back before installing SS exhaust tips. I think this link will work since I could not get it to load under attach files since I must have previously posted the picture. Bill

http://www.donzi.net/forums/attachment.php?attachmentid=28858&stc=1&thumb=1&d=1178645917

[The Hedgehog]

Big Green,
I have a 1985 23' Eliminator Daytona with a 468CID BBC blower motor probably making only about 600HP with 7.5 lbs of boost. I had to design a custom made 1/2" aluminum plate which I attached with SS button head bolts through the transom to accomodate the new Bravo drive assembly from the previous Volvo Penta which would not take the HP. I set the drive with the maximum X dimension to still get the boat on plane. It is set at about 3" higher than the maximum Mercruiser states is the highest after talking to some speed experts in Florida about 10 years ago. Here is a picture taken a while back before installing SS exhaust tips. I think this link will work since I could not get it to load under attach files since I must have previously posted the picture. Bill

http://www.donzi.net/forums/attachment.php?attachmentid=28858&stc=1&thumb=1&d=1178645917


Very nice. That looks like a blast.

[Conquistador_del_mar]

Very nice. That looks like a blast.

I get a kick out of restoring older boats and cars and modifying them to my preferences. I derive a lot of satisfaction from driving these older vehicles that I have spent so much time making the way I like them to look and perform. Don't get me wrong - I really like new advancements, too! I can't tell you how many times I have come into the ramp or pulled into a gas station with people coming up saying "that is one of the best looking (cars or boats) I have ever seen". That is when I really feel my time has been well spent. I will never forget the first time I took my present girlfriend of 12 years now out in the Eliminator for the first time. She turned to me and said "everybody in the marina is looking at us". I turned back to her and said "no honey, they are looking at the boat" - lol. Bill

[Conquistador_del_mar]

Very nice. That looks like a blast.

Big Green,
Here is a bow view I took a couple years ago. I need to get some better pictures taken. Bill

[The Hedgehog]

I get a kick out of restoring older boats and cars and modifying them to my preferences. I derive a lot of satisfaction from driving these older vehicles that I have spent so much time making the way I like them to look and perform. Don't get me wrong - I really like new advancements, too! I can't tell you how many times I have come into the ramp or pulled into a gas station with people coming up saying "that is one of the best looking (cars or boats) I have ever seen". That is when I really feel my time has been well spent. I will never forget the first time I took my present girlfriend of 12 years now out in the Eliminator for the first time. She turned to me and said "everybody in the marina is looking at us". I turned back to her and said "no honey, they are looking at the boat" - lol. Bill

Restoring older things to your preferences:beer: That's what it is all about. I had a 66 Mustang in high school. I really like the look of a coupe vs the fast back. It was a 6 cyl and not so rare. Why not do some mods? When I was done it had a built up 302 and a bunch of Shelby's effects. It basically looked like a GT 350 but a coupe. No, I did not call it a GT 350 but I did borrow some of the styling along with my own. Had it been a rare 289 High Po, I would have done it all orig. The way I ended up doing it was way more fun. I am sure that some purists would cringe but I can't tell you how many thumbs ups I got at traffic lights. From then on it the sickness continued! Now its boats!

[Conquistador_del_mar]

Restoring older things to your preferences:beer: That's what it is all about. I had a 66 Mustang in high school. I really like the look of a coupe vs the fast back. It was a 6 cyl and not so rare. Why not do some mods? When I was done it had a built up 302 and a bunch of Shelby's effects. It basically looked like a GT 350 but a coupe. No, I did not call it a GT 350 but I did borrow some of the styling along with my own. Had it been a rare 289 High Po, I would have done it all orig. The way I ended up doing it was way more fun. I am sure that some purists would cringe but I can't tell you how many thumbs ups I got at traffic lights. From then on it the sickness continued! Now its boats!

I agree entirely. Modifying a car or boat without a huge collector value is one of the most fun things I have done. There is really no sense of satisfaction like driving something you personally did all the work on. I respect the men who successfully modify vehicles even if I personally would have done something different. A few years ago, I sold a 27SS Cigarette to a local man. It needed everything. He showed up about 9 months later with a totally radical modified restoration that was awesome! He said "you didn't think I could do it - did you?" I told him that I did have my doubts, but that I was wrong. I'll bet you sometimes wish you had the '66 Mustang back. Bill

[Tony]

You must break the stiction layer for maximum performance.

Phil, you crack me up with your creative vocabulary!


:beer:

[The Hedgehog]

I agree entirely. Modifying a car or boat without a huge collector value is one of the most fun things I have done. There is really no sense of satisfaction like driving something you personally did all the work on. I respect the men who successfully modify vehicles even if I personally would have done something different. A few years ago, I sold a 27SS Cigarette to a local man. It needed everything. He showed up about 9 months later with a totally radical modified restoration that was awesome! He said "you didn't think I could do it - did you?" I told him that I did have my doubts, but that I was wrong. I'll bet you sometimes wish you had the '66 Mustang back. Bill

No, I should never sold it. At the time I was a college student that needed a set of wheels that got good gas mileage and had an A/C. I basically traded it to my father for a Ford Ranger:smash: He had a bunch of cars so he sold it. About five years later I really regretted it.

Another Bill

[MOP]

Of course at 100+ I'm sure it makes a difference, on our boats, I'm not so sure it's measureable.
As for engine ports, I agree 100%. The old "ported and polished" comments give me a good laugh.

Dennis Conners gained 2/10 of a knot at Freemanlte during the Americas cup sail boat races by applying the Boeing rivlets which benefit jets at high speed. On my race boat I gained by not sanding the bottom baby smooth, I instead went to a stipple which helped me to grab the Block Island trophy. That trophy in my area is a big feather in your hat, I wish I had know about it when I raced Stars although I would have been disqualified but would have had some fun with the fleet.