Engine Options
 

Cracked block, and need to change it out. I was looking at short block options also. Should be an interesting Poll. The least expensive will be the 1st option and going up from there.

Boat is a '83 Donzi Classic 18'. 350ci engine pushing 350hp. Bravo 1 Drive " higher x-dim than standard
Getting 70@5000. It will do close to 75 if I want to push the rpms.

If I go the short block route, I have heads, intake, carb, cam to match the flow needed. Stringers are HD and have External hydraulic steering.
Yes, I want more speed but want to maintain good handling.

18 classic

Bravo 1 Drive, 2" higher X-dim than Donzi Standard.

I love the Donzi Classics and have owned many over the years. Fun little hot rods.

If it was mine I'd put a HP500 in it......


Just because it will fit :D

Get the best you can afford! :eureka:

...and if you run aluminum heads and CMI's it wont weigh much more than the stock 260 Merc with all the cast iron junk.

There is no replacement for cubic inch displacement!!!

I'd stick with a small block in the 18. I'd go with a 350 mag set up for a blower or maybe the merc scorpion if you have the $$.

go big or go home :)

Current engine...

Go with a large c.i. small block. 406 is pretty easy. With World Products stuff 427c.i. / 500hp is not too expensive and all of your accessories still fit.

After seeing the current engine, I take it keeping it below the hatch isn't a concern!:)

383 Stroker!!!! :D

better put some wings on that thing too :) thats really going to be something when its done.

Kent,
A 502 is tempting, but then you start talking a lot more $$ for things like exhaust, and all the other bits you'd have to get. Ive heard of some pretty nice 383s being built that can see 450+ reliable HP. Although the guys that brag about the reliability, never mention it a week later when they break. If i recall, that motor is pretty new, and you have a lot invested in it, so reusing a good amount of parts is nice, if you can do it. That 18 may sit a bit low with the BB in it. I have a 502 in my criterion, and THAT sits pretty low at the stern.

Any idea what went wrong with this motor?

Hey Kent,
Isn't that an AlphaSS drive in 1st pic? I thought those Donzis came with SS ... though maybe I've got the wrong year and I'm :confused: :confused: :)

Not an Alpha SS. Old stlye Bravo 1 with a Nose Cone.

McGary911 - The crack is from a helicoil in the deck to the water jacket. Minor, but enough to let water through. The block has a lot of hours on it even though it was freshed about a year ago.

22 votes for the 383
20 votes for the 502.

I'll split the difference and go with a 406.
6" 4340 rods, lightened forged crank, JE pistons, internally balanced 9.7:1 compression and using my Sportsman II heads and lopy cam. I should see a slight increase in HP and Torque.

I do like the idea of having the big cubes in the small boat, but then I'll have to put a bigger tank in.

I'll save the bigger motor for the next project. Also with the smallblock, I can put those 283 ci stickers on the flame arrester; and until I crank it up.... lol :)

A buddy of mine has a 383 with 475hp in a 21 minx. He loves it and it is very reliable. It runs 77 all day.

probably look pretty neat with a canopy too.....

A couple of you mentioned 406. I assume you're thinking of using the siemesed bore 400 SBC block. I don't recommend this with a salt water open cooling system. The steam holes are too small and would be easily clogged with corrosion. They can NOT be drilled oversize either because of their proximity to the head-bolt hole. Also using this block would require you to have your heads drilled with steam holes. Using the 400 small block IMHO would not gain you enough extra power over the 383 to justify the added cost, not to mention your reliability would be down the drain. If you want to stick with a small block I suggest the 383 with 5.7 rods. Go to the extra expense and opt for the steel crank I have built many of both motors and there is no discernable power difference when built right.

Roby

Stick with the small block!! :D :D only those ole guys run them big blocks ;) :D Last year I ran the 383 with a little over 500 hp, only thing I had to do with this motor was change the oil, never any problems :)


I'll be around 560-570 hp on my 383 this time around, running 110 octane ofcourse.

I have a Minx that I'm building about a 340 horse 350 for.

i had a 99' 21 foot donze classic...it waqs so dangerous. when u turn it leaned so far to the side that either the driver or pass was gettin wet...sure the boat was fun, but safety wqas minimal..the boat woudl take air all the time. we had a 454 and it only went like 65 and it was a scary ride...there is a 502 with blackhawk drive on our lake...it looks awesome, but i dont know a ou tthe build

we used to own the late 70's and early 80's 16'. 18' donzi's, and these boats were really solid...knockin on these new 21's u can feel that it is not solid...the classic line build today is nowhere near the quality of the old models....

justin

hey kent, could you post some pics of the boat. im looking for one just like that. i love the paint on that. post a few, love the lines on those classics donzis. Mr.Wonderful

Kent,
I have to agree with Roby, stick with the 383... you'll be much happier in the long run.

stecz20 -

Here is a side shot before the drive change last year.

Already scooped up the 406 block. I mostly run in fresh water and never had much of a corrosion problem. (The last block lased me 10 years) The cost difference in a full 383 forged shortblock to the 406 was the same and the block is in perfect condition.

434!!!!!!
 

ahhhh bummer kent... when i find that right 18 barrelback there will be a 434 tucked neatly under the hatch.

til then welp i'll just have to be content with the 350 in the 16 :D

www.shafiroff.com

Rootsy

Ahh, no replacement for cubic inches!!

Got the 406 in. Sounds like a 350 at idle. Time to plane depends only on how quick your foot is (foot throttle). Accelleration is FANTASTIC! It will spin the 23 Mirage to the rev limiter (6K) in a matter of seconds...

I'll be trying the 25 next weekend.
Think I'll be needing K-planes next...

Congrat"s on getting her back together.Yes,pix needed.Your boat is still one of my favorites.



Ken
(KMLFAMILY)

Actually looks just like the engine picture earlier in the thread. Going to take a few pictures running this weekend. I'll post them.

Ahh, finally a picture of the new "260HP" :D :D :D

I only have a few hours on it checking jetting and just tooling around. Not sure how fast it is yet, but it will do a solid 75 on the "Livosi" before the kids start begging for mercy. Have not been out by myself, but I think it will be finally fast enough for an 18 after I get the prop labbed. Accelleration is fantastic and will spin a junk 25 Mirage to 5K almost before you can back off..

A few minor cosmetics on the deck, new seats and time to start on the next project...

AMEN:D

Very nice, Classics are a great hull. I am selling my Sweet 16 later this week. I am going to miss that thing!:(

I didn't say at what RPM the 260hp came in :D :D :D

Kent, Look's great. I think you should have put the 572 in it tho.......:rolleyes: :rolleyes: :crazy: Dave

Yeah, that would be an eye opener at the ski club :D :D :D

Re: Engine Options
 

Way to go, Kent!! The boat looks great!