1974 X18 weight and prop questions

[Rob Birch]

Other then standard annual maintanance I have been running my 1974 X 18 virtually unchanged for the past 23 year. This winter I have tweaked the small block 350 to 300 hp. The outdrive is a 270 VP. First I am curious to know the weight of this boat because it feel much more heavy then my buddy's 1989 18 ft classic which is 2700 lbs. Secondly I still have the original bronze prop on the outdrive and I know that prop selection is a matter of "try and see" but can someone help start me in the right direction prop wise?

[John C in PA]

Hey Rob. A good start is to provide the ratio on the drive, the prop model, diameter and pitch, and what revs you get at WOT. Others will help you with the weight.

John C

[dsparis]

Hey Rob, get ahold of Mr Fixxall on donzi.org. He's got a x18 and knows them inside out.

[mattyboy]

the volvo adds some weight, that setup needs a 21 solas titan or a 24 ultra. the solas will run right out of the box, the volvo ultra prop will need the hub modified the stock hub was weak it needs a michigan hub pressed into it the stock hub is prone to spin with high HP, mr fix also has a prop guy that basically labs the ultra to get the most out of them.

I also show the gross weight of the X at 2500 lbs and the late 80's vintage of 18 at 2250lbs a volvo aq is heavier than an alpha, a boat with trim will also appear lighter as it can be aired out more than a non trimable 270.

is this a chris craft setup??

[Kirbyvv]

I agree with Matty. I've run a Solas 21, Ultra 24 and also a Michigan SS 21 on my '78 X-18 with a volvo 280 drive. The Solas is the only prop available on the market now, but the ultra's and Michigan's turn up on ebay occasionally. I was lucky enough to find 2 new Ultra 24's last year, thanks to a lead from someone on this site.

[Marlin275]

What is the real world difference between the Solas 21 and the Ultra 24 in performance?
I have never understood the qualified answers given.

[mattyboy]

Marlin,

I can only speak from the extensive testing on did on my 16 and the 19 cig both were volvos with no trim.

I ran a custom prop 21 spinneli SS and the boat was a handful at high speed best useble speed was around 52-54 mph then it had a mind of it's own, out of the hole it was a beast it planed in no time and would never blow out. I then got a 22 ultra it was a little faster maybe 55 mph before it became a handful . i could get to about 57 in the right conditions for a few seconds before i soiled my swim trunks. I also tried to run a 25 chopper and a 26 clever 24 ultra all with the same bad handling quirks. either torque steer chine walking ventilation blow out you name it they had it

I had the ultra re hubbed it spun on me then i got the solas 21 from Grizzly it was an early one with some tweaking it handled like the boat was on rails in any water conditions would not blow out and was hooked to the water. when pulling out of the throttle quickly it was like a chute was deployed. it planed quickly and gave me a useble WOT I could hold the throttle down as long as i wanted my best run with the solas was 62 mph.


it by far was the best investment i ever made in the performance of the 16 and was the second biggest improvement to safety right behind replacing the fuel tank.

I would highly recommend the solas titan to any volvo aq driven classic. the prices are reasonable and they make a great prop to run on a daily basis or as a backup to your lucky prop in case it fails.

anyone who has tried one like the way the perform ,the only negative i heard was from a very few who like alot of bow lift. the solas carries the entire boat at a great angle that lets the hull do it's job and let's the motor put all the power to the water.

the results were the same on the 19 cig as well.

maddad and magicbill run higher hp volvo setups they have tried the solas with about the same results.


the real difference between the two

the ultra will be a tad faster but will have a ventilation and blow out problem in rougher water. they were more expensive $400 + and harder to find in the 24 and 26 lh models but they do show up every so often . the stock ultra will run about 12% in slip and may go a little higher the faster you go . I have seen the prices come down some recently

the solas has come down in price and you can find them for around $300 they will not ventilate or blow out in rough water they will run about 7-8 % in slip and can be found online pretty easily.

we would not have these props if not for the hard work and dedication of Randy Big Grizzly. RIP

[Rob Birch]

Thanks guys for the info. I will find out the drive ratio but I am pretty sure it is stock as I have never messed with it other then replaceing parts. I will try the solas first. As you know my outdrive has no trim. I made some bushings that the pin threads through to increase the trim further when the pin is in the 3rd hole. My question is... Can I increase the trim in this manner without harming the universal in the 270 or should I just keep the pin in the third hole. I can tell you that the boat gets a bunch more lift and speed when the bushings are in place... maybe 4 - 6 mph but maybe the 270 wasn't designed to be trimmed out that far.

[72Hornet]

I bought two Solas props for my Hornet from Griz a 19 and 21, 270 Volvo Drive, (no trim) original 350 Chris Craft conversion, 320 hp. The 19 gave me great hole shot, but over revved. I tried the 21 and the difference was incredible! It really woke the boat up. gave me a little bit more bow lift, but stays connected to the water. Still has good hole shot, higher top end speed and a safer feel at the helm.

[Marlin275]

Matty thanks for your in depth analysis.
I have a 26 Ultra and have never had any handling or steering problems (stock internal hydraulic), when the drive is in the middle pin position.
I get about 4400 RPM and about 58 max mph.
I am always looking for performance improvements but don't want to get a new drive now.

The Solas seems to improve handling issues well but the Ultra is faster.

[mattyboy]

Bingo!!! thanks Royce that pretty much wraps it up.


I have a 21 and a 23 solas but have not yet built enough power to turn them I am using a 21 spinelli and will try a 19 solas in spring .

with the bushing yes i guess they can stress the u joints if the drive is trimmed up but no more than a 280T with trim would and if the boat runs better with them I would not worry about it , only when and "if "they fail.. If you try a solas or an ultra you might find some bow lift and not need the bushings the 3rd hole may just be the sweet spot.

[Just Say N20]

and will try a 19 solas in spring.

Which reminds me. . . .

. . . . I will send you the 19 Solas. You are likely to be able to see if/how it works before I get to trying either of the props you sent.

I did purchase a 23 Solas Titan based on everything I read, and suggestions for a couple people on the site who run them. Hard to test them until the engine/drive are completely reinstalled.

Lots of interesting information to follow.

[mattyboy]

Marlin
you are right in the ball park for an ultra those numbers you are running at 14.3% slip not very efficient

if you could turn a 23 solas to 4600 rpm you would be around 61 mph but you would be surprised how hard it is to turn a 23 solas

[mattyboy]

Bill

not to worry when it warms up in spring you can send it .
I still have some tuning to do on mine and the way it looks with Marie's shoulder surgery I am going to be at idle speeds most of the summer. but a slow day on the boat beats the hell out of no day on the boat.


yes the 23 solas will be a good prop in your stores they act much bigger and really grip the water if you can find a 26 ultra too. I'll keep my eyes out for that . looking fwd to seeing some of your numbers .

[Rob Birch]

You guys are great. Thanks for the info.