Custom built Sweet 16

[Last Tango]

So...
I wuz sitten here thinkin' I might need a second boat just to play with at certain venues, and also to try to do my Eco-best, and to protect manatees and such.
So...
I thought a brand new Sweet 16 would be fun. I have had one before.
But with THIS in the engine bay:

http://www.mercurymarine.com/engines/jetdrives/250optimaxm2_specs.php

Any reason this would be a bad idea?

Remember, I already have a 2006 22ZX (see signature below), and I plan to keep that as well.

[Formula Jr]

Wouldn't a Medallion 152 (http://www.donzi.net/photos/osaffell576.jpg) be easier???


:wink:

[BUIZILLA]

My Sugar Sand jet boat, same as Phil Reed's, had a 175 MercJet, in 2' or less of water it literally vacuumed the bay bottom, rocks and all... :bonk::eek!: also, it used TWICE the amount of fuel a normal 175 would use, and it was terribly inefficent, very smooth and quiet though....

but the FUN FACTOR was off the charts :hyper::hyper:

I see your choice has DUAL 3" thru hull exhaust with mufflers?? how cool is that.. :yes:

[Just Say N20]

It would be a fun project. With that engine I would guess a top speed in a 16 to be around 48 - 52 mph.

I have a 14', closed bow jet, with 19 degrees of deadrise rather than 24 like the 16. I did an engine/pump transplant a couple of years ago, replacing the Mercury Sport Jet 90 with a Mercury 175 Sport Jet. Here is a link to the project, if you feel like reading. My boat runs 50 GPS mph with just me in it. Weight has a pretty pronounced affect on the performance.

www.realityboatco.com/RBCtalk/viewtopic.php?t=14

It is a fun boat, and I think a 16 w/the 250 would be great fun. The 250 will burn about 23 gallons per hour at WOT, so it will go through the gas pretty well if you have a heavy foot.

http://i26.photobucket.com/albums/c111/streb2005/ReflexxShinyNoPlate.jpg

http://i26.photobucket.com/albums/c111/streb2005/ReflexxPortquarter-1.jpg

[Last Tango]

Just Say...,
WOW! Excellent link to your project. I read the entire thread, ran the movies. I was very pleased to read the outcome and see the posting of your performance numbers, including the link to the fuel consumption.
Fuel consumption is an important part of the equation, particularly in these times.
You never did mention if you finally sold the boat.

I want to start with a brand new Sweet 16 for several reasons:
1. I want the FACTORY to do the installation. My real forte when working with tools around mechanical things is to sign the credit card receipt.
2. Warranty
3. HP to weight ratio - 250 Optimax M2 Jet Drive is much lighter than any of the normal engine choices for a Sweet 16, and more powerfull, and smaller.
4. Heavy duty, offshore hull design of the Sweet 16.
5. Seating for me. Period. I will have the standard single seat replaced by a custom recovered Recaro race seat to match the L-couch. Should also help to lower me a bit more into the boat so I feel more like I am IN the boat rather than ON the boat as is the case now with the standard seat.
6. Start with an uncut dash and eschew the traditional gauges completely. Instead, take maximum advantage of the SmartCraft System Montor and all possible peripherals. Then, a VHF radio and AM/FM/CD, over/under.
7. Grab bar - no windshield.
8. Custom graphics in the gelcoat.

Totally 21st Century technology in a classic hull.

Absolute top speed is not the goal. The weight reduction and increased HP should still keep it in the mid-50's.

[boxy]

Mark, we have all already had this conversation ... :D
You need to start using your bimini more.
http://www.donzi.net/forums/showthread.php?t=46629&highlight=mercury+jet

I still think it's a great idea ......

[pmreed]

All that Jim said is true. Fun boat, top speed GPS about 52. But, a gas hog. I could burn up the 20 gal tank in under two hours without even trying. Of course, that's with the carb 175 motor. I can tell you this; if I had the same hull design as the Sugar Sand with a straight outboard, It probably would have hit well over 60, and at 40 would have used half the gas. Jets are just inefficient as all get out. And yeah, had to clean the clams out of the intake grate every now and then:).

Phil

[Last Tango]

Yes, I know we only just last year talked about this, but I wanted to recycle the thought. It seems so intriguing that I hope Donzi will pick it up again.
Sometimes you have to think about the past to improve the future. Sort of like Electric and Hybrid cars. Folks act like this is all new, and in fact there were dozens of manufacturers of electric and hybrid powered car over 100 years ago.

[Just Say N20]

Computers are a wonderful thing.

I was thinking we had gone through this before. I would like to see one one these done with a Sport Jet, even if it is someone whose mechanical expertise is "signing the check."

I still have the Reflexx. I bump into a couple of the MI guys in their 22s almost every week end during the summer on White Lake. I works well in protected waters, and is a lot of fun. :nilly:

[yeller]

Dooooo iiiiitt! The 16 loves the jet. A few mph slower than a prop, but waaay more fun. Never, ever, spun out once and I used to go flat out then crank the wheel all the way. The hull would just dig in, turn around, and then pop up like a cork and blast off! I miss my 16 jet sooo much.

That motor should put you close to 55mph. My 1st engine was an old stock 350 which was probably under 200hp and it gps'd at 50. Also that motor will mount low in the bilge because of the jet, so you'll have tons of access room.

[Last Tango]

Thanks, Yeller!

A general set of common questions popped into my head about this:
Looking at the Mercury Marine photo and specs of the engine, it talks about the drive unit. Is that a separate piece, or am I seeing the whole thing in those pictures? Is there more, like when you look at other Mercury engine pix and they are separate from the outdrive pix? Is there something mounting to the stern like the Berkeley drives, or is it like the jet ski setup where it is flush to the bottom? If it is flush, how do you direct the nozzle to steer? Will there need to be more to the "hole" than the intake/exhaust nozzles? Hard for me to picture how that will work/look on such a sharp deadrise. I can picture the credit card receipt, but not the actual bottom configuration. LOL!!!!!

I read through all of Just Say N2O's post on how he did his upgrade. Fascinating. But mostly his project was stuffing 10 pounds of sh** into a 5 pound bag, rather than converting engine and drive systems from one type to another. Still, it was very interesting and very incite-filled. Probably the best "how I did it" post I've ever read. Awesome photos and updates.

I am not planning a conversion from an existing boat, but from an uncut hull at the factory. I just have such fond memories of my first Classic 16 (bought new in 1999).

I once owned the Worlds Most Expensive Classic 18. Perhaps I will now own the Worlds Most Expensive Classic 16. LOL!

[BUIZILLA]

with a round bottom hull, how does the flat jet baseplate coordinate itself??

[VetteLT193]

Merc takes an outboard and modifies it into a Jet. This means the crankshaft is vertical instead of horizontal, which of course requires a 90 degree turn to get the power to the drive. The main area that a jet drive gains back efficiency is in the direct drive setup, but Merc continues to negate that advantage.

I think you'd be better off with a Rotax (Sea-Doo) engine, or go with a Berkeley setup.

I always thought a Sweet 16 would be kick butt if it were set up with twin jets like the old Sea Doo speedsters.

I used to have a 1994 speedster (got it new), and it was a TON of fun (If I remember right it had near 700 hours on it when I sold it in 1998). It was the hay day of jet boats in the 90's and I had a few friends that bought them too... The Merc boats got out-performed by Sea-Doos in every way.

BTW, one problem you might have with a lighter jet engine setup is the hook in the 16's hull.

[Last Tango]

Buiz,
I think you have actually stated my question in a whole lot less words than I used.
Just Say N2O's pix from his project show a rather defined box recessed into the hull, as well as some sort of "ramp" the Bayliner folks added to the bottom. Such a ramp would be difficult to add to the V-shaped Donzi, unless the V itself was considered to be the ramp. In this case, the drive would be sort of recessed by the mere fact the the V would extend beyond in front of the box. I guess I need to stop by the SeaDoo dealer and look underneathe one of their boats.

[BigGrizzly]

If I were to do this project I would use a 4 stroke engine or maybe even a diesel. True the manatee would only get a headache, however you would have to convince the DNR people. The air boat guys didn't do to well at that point either, when they tried to suspenf the speed limit for them either.

[Last Tango]

Vette,
I have also pondered a PAIR of 250 Optimax M2's in the engine compartment of a Classic 22. 500 HP! Woo-hoo!!!!!!!

[VetteLT193]

If you are interested in a sportjet, you should really find a Sugar Sand dealer. They use Mercury. Sea Doo is a totally different beast.

The Merc unit is more of a stand alone setup, the intake and pump is one big 'box' of a unit, all that really needs to be done is the proper holes cut. (big rectangle in the bottom for the intake, plus a 'box' in the transom for the nozzle to go through

Sea Doo is more integrated into the hull, a lot more glass work would have to be done on the bottom, but would 'fit' the hull much better over the Merc 'box'. Sea doo jet pumps are mounted flat on the transom, like a stern drive, instead of being boxed in, because it is a stand alone part instead of the one large box unit.

[Just Say N20]

You would most likely not need the "pre-load" hump like the one on my project.

Each jet drive package will have a very specific cavity that will have to be retroactively installed in the hull to accommodate the pump assembly. The Mercury Sport jets are mounted into a box shaped area.

http://i26.photobucket.com/albums/c111/streb2005/Humpfrompumpcavity.jpg

Like every other decision, there are going to be pros and cons to each available system. While the idea of putting a Sport Jet type package in a 16 is intriguing, I would be concerned about the balance of the the boat, and resultant handling because there would be about 600 lbs LESS engine/drive weight in the back of the boat. In a 16' boat that could be disastrous, causing the bow to run very wet, with a tendency to bow steer.

If it were me, I would do a V8 jet package. Tight fit, absolutely, but it has been done before with very good results. And, you get "The Sound." :yes:

I did find a company (in New Zeeland) that makes a trimmable nozzle for Sport Jets; retail is $2,000. Here is a link to some videos. http://www.princegeorgeyamaha.com/scott_jet_boat_nozzle_videos.htm

[VetteLT193]

Vette,
I have also pondered a PAIR of 250 Optimax M2's in the engine compartment of a Classic 22. 500 HP! Woo-hoo!!!!!!!

IMO, if you are looking at a sport jet, cut the HP number in half to get a comparable outboard number... For I/O purposes (to overcome the weight) I'd say twin 250 Sport Jets would be roughly equal a 300-320 HP Small Block w/Alpha 1 drive.

[Last Tango]

So then, maybe, I should forget about using the Mercury Jet package to save weight because of the imbalance it may cause in the hull design, and stick with the 5.0 V8 option and see about a Berkeley-style add-on thruster. I thought the substantial weight reduction would be an excellent trade-off for whatever efficiency losses there may be for not using a conventional prop.

This boat would be for lakes and rivers, not offshore or Tampa Bay.

Again, a major goal is to NOT be swinging a razor sharp high-speed guillotine 2 feet under this boat.

[VetteLT193]

So then, maybe, I should forget about using the Mercury Jet package to save weight because of the imbalance it may cause in the hull design, and stick with the 5.0 V8 option and see about a Berkeley-style add-on thruster. I thought the substantial weight reduction would be an excellent trade-off for whatever efficiency losses there may be for not using a conventional prop.
This boat would be for lakes and rivers, not offshore or Tampa Bay.
Again, a major goal is to NOT be swinging a razor sharp high-speed guillotine 2 feet under this boat.

The weight reduction is great, but the efficiency of Jet (especially sport jet) negates it again.

A 5.0 or 5.7 with Berkeley would be a FUN ride. I'm thinking even a 6 cyl. would do you good depending on how you intend to drive the boat. The odd thing about most jet setups is extra power doesn't usually yield much top end, but it will give you a ton of extra acceleration.

I'm going to guess that a Merc 4.6 would give you a top end about 45-47, 5.0 would be right about 50, and a 5.7 would be low 50's. The biggest difference between those 3 engines will be your 0-20 and 0-30 MPH times.

I guess before I rant on I should ask if you have driven a jet boat before?

[Formula Jr]

Wouldn't putting a 250 Optimax M2 in a Donzi Medallion 152 be easier?
Instant Sprint Boat.

You could also see if the Verado 300s had a jet drive lower unit available. Run it by the Coasties and see if you can bolt that on to a 16C O/B.

[Last Tango]

I owned a Regal Rush XP with 120hp Merc jet from 1997 to 2000. The boat I traded it in for was a new 1999 Donzi C16 with a 190HP 2bbl V-6 and Alpha drive which I owned for 6 months until I again upgraded to a 2001 C18 with the MX 6.2 MPI which I kept alongside a couple of other Donzi cruisers (28 LXC, Z3250 Daytona) until last year when I traded up again to an '06 22ZX with 350 Mag MPI with Bravo One drive. I LOVE the 22ZX and am quite proud of it and plan to keep it for a while.
The Regal Rush XP wasn't much of a rush. It topped out at about 40 MPH but was really too small to enjoy the ride. I did not venture out much onto the St. Johns River with it, but remained in the safety of a very large creek called Julington Creek. Plenty of long wide water to play with in there.

The concept of cross-breeding a Donzi and jet drive have been with me since the C16. There are plenty of existing Donzi jet drive boats so it isn't some weird foreign concept.

[smokediver]

Hey Mark , I used to have a boston whaler rage . not the little 15 but the bigger 18 foot . Looked just like the Ventura Bowrider line. It had a Redline 351 carbed rated at 275hp and an American Turbine jet with a Jet-A-Vator trim nozzle . The boat ran real well , not a fast boat by any means but it ran about 45 mph with that setup . There is a fine line between shallow running and vacuuming the bottom !!! lol ... sounds like a great idea ! I would go with the Berkley as they are the biggest supplier and get a Place Diverter or jet-a-vator ... just like trimmg an i/o but a lot of rooster tail ...