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Thread: Need Prop Advice for a 73 X18

  1. #1
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    Need Prop Advice for a 73 X18

    I read some great content about this subject especially from Big Griz. I have an all original 1973 X18 with a recently re-built 350 Chevy 300+hp through a Volvo-Penta 270 no trim of course. I am thinking of going with a Solas SS and can't decide between a 21 inch and 23 pitch. I don't pull skiers so don't care about coming out of the hole. I like a high bow ride and run this boat on an inland lake so not concerned about going too fast. Biggest wave I see is from someone pulling a wake boarder.

    I am getting to about 52 mph GPS at 5400 RPM. Would love to approach or hit 60 mph. A little blowout occasionally is okay.

    I would appreciate any good suggestions. Thanks!
    Ted

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    I ordered two Solas Propellors from Griz on my Hornet 19, original stock 350 GM 320 HP that runs strong. I ordered the 19 and then talked to Griz and then ordered the 21. The 19 gave me way too many RPM's, but really woke up the engine. The 21 seems to be the sweet one for my boat. It has nice hole shot and gives me fairly good bow lift. For performance, I really do not like to rev the boat that hard on wide open, but it hits 5000 and that is plenty for me. I guess that I would try the 21 first and go from there. It would be so nice to have both props side by side so you could see the results right after another. I love how it made my Hornet perform. (now you have me thinking that I should try a 23!) Good luck and let me know how you come out!

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    21. 19 Solas won't be enough and you need a lot more hp to turn a 23.

    I know of a few people with Classic 18s with over 350 hp running the 23.

    I bought a 23 for my 16, with over 430 hp and 500 ft lbs. Volvo 290 with trim.

    I will let you know in the spring how it runs.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

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    With 430 hp in your 16 and a Volvo 290 with trim, that will be wild! My 19' Hornet is a big boat and alot of hull to push without trim. I have the 270 Volvo drive that is original to the boat. It is a rock solid drive, and I often wonder how much that hull and engine combo would awaken if it only had trim! At it's current state, it is a blast to drive, fun in rough water and turns alot of heads. The flared bow gives a very dry ride with a soft re-entry when I air it out a bit. No better feeling! Nice job on your 16' restoration BTW!

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    Solas 21 - how order?

    This forum is great, thanks guys. I just joined and can see already this is going to be fantastic.

    So it looks like a 21 inch pitch is the right one for me, maybe 23 but not for now. Couple questions... I know I need a LH prop and know I want SS. Is Solas the best or only choice? I saw some mentions of Ultra. Do they come cupped for bow lift or do I need to specify that? How do I get the right hub type? It is NOT through through hub exhaust, right? Is it long hub shaft???

    I just want to make sure I get the right kind for a 73 Volvo-Penta 270.

    Thanks!
    Ted

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    That will be crazy

    16 with a 23 pitch and that much hp plus trim?! That will be unreal. Let us know. Take a video of that too.
    Ted

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    73X18, Go with the Solas, Griz worked with them and got the Solas family to specifically design that propellor to the Volvo outdrive. I met all of them at the Miami Boat show back in 2007 or 2008. I too have the Volvo 270 outdrive and think you will be very impressed by the 21 and what it does to your performance. I had to have my prop shaft drilled and threaded to fit the Solas to my Volvo outdrive. I would send pictures, but I am layed up for a few weeks. Just had a tendon repair on my knee, so computer is my relief for a month or so...
    Griz was a great friend and help to the Donzi world... I enjoyed his enthusiasm and his historical perspective on the marine industry.

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    Thanks for the help and sorry about your knee.

    Can you give me a little more info on what was necessary on your prop shaft? I was hoping I could just put it on. What did you have to drill? Does it hurt the ability to use the original style props again?
    Ted

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    I did a lot of testing for Griz on the solas it is for sure a prop to have in your arsenal.

    the Volvo AQ had two different Hubs long and standard( sometimes called short) with the right equipment both hubs can be run on both shafts.

    first you will need a few different length thrust washers , you might need to drill and tap the shaft for the prop cone bolt, and you might need to address the clearance of your torque tab/fin.

    the thrust washers space the prop and you will need to get it out far enough away from the shaft anode not to hit and in far enough that the prop nut has enough thread to bite and hold. the later is the part where you have to worry about the torque tab.

    the attached pic might help. Also iI wrote a thread on the other forum some 6 years back not sure if it is still there or not, on my solas testing. It has some info and part numbers on an torque tab that will work.
    I don't own the 16 any more and my new benchseat is a volvo , it was second nature the solas went right on as soon as i got the old prop off.

    I had a few very long thrust washers i had a friend cut them into a few different sizes with a little change I could run any AQ prop i wanted and I had A LOT of props before I found the solas.
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  10. #10
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    Quote Originally Posted by mattyboy View Post
    I did a lot of testing for Griz on the solas it is for sure a prop to have in your arsenal.

    the Volvo AQ had two different Hubs long and standard( sometimes called short) with the right equipment both hubs can be run on both shafts.

    first you will need a few different length thrust washers , you might need to drill and tap the shaft for the prop cone bolt, and you might need to address the clearance of your torque tab/fin.

    the thrust washers space the prop and you will need to get it out far enough away from the shaft anode not to hit and in far enough that the prop nut has enough thread to bite and hold. the later is the part where you have to worry about the torque tab.

    the attached pic might help. Also iI wrote a thread on the other forum some 6 years back not sure if it is still there or not, on my solas testing. It has some info and part numbers on an torque tab that will work.
    I don't own the 16 any more and my new benchseat is a volvo , it was second nature the solas went right on as soon as i got the old prop off.

    I had a few very long thrust washers i had a friend cut them into a few different sizes with a little change I could run any AQ prop i wanted and I had A LOT of props before I found the solas.
    Just installed a Solas on my standard hub 270. Used the thrust washer (A) that was used with the original prop, the propeller cone (D) and allen bolt (E). Do I need a washer (B)?
    Patrick

    1968 Donzi Ski Sporter C16-512

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    73 your looking for a solas titan 3 blade if your helm is on the left order LH

    Sandog, I use a threaded washer and a nylock nut with out the cone , with the cone i would use the washer for a snug even fit.
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

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    Come Join Us on The Queen Of American Lakes



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    Thanks Mattyboy- great info, really appreciate it.

    i have seen conflicting opinions on how many RPM's I should be running wide open. It's a rebuilt Chevy 350 Chris Craft marine engine so it is built to run faster than if in a car right? My mechanic felt 5400 RPM WOT was fine. Others have written indicating that is too high. I realize a bigger pitch will drop the RPM. Maybe others comments are base on MPH versus dangerously high RPM?
    Ted

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    I think MOST marine engines are built to run at higher AVERAGE CONTINUOUS RPM (AKA: cruising RPM) than are most car engines, but not higher peak RPM. A boat might well run at 3600-3800 for very long periods. A non-racing car is not likely to see that sort of sustained load.

    And when I say "built" I'm thinking high-temperature valves, enough cooling to dissipate the heat, a torque curve with enough grunt to get up on plane at low RPM, and...I'm not sure what else. And even with such things in a marine motor, that only prevents it from grenading right away. It's still going to suffer a lot more wear than most car motors and the life span before rebuild will be far lower no matter what.

    So, with all that, if your motor is a Chris-Craft-marinized offering that's been rebuilt per stock specs, 5400 sounds high to me. Without a cam swap, I'd think you'd be well down on torque up there and noticeably below peak power. 4600-5000 would be more my expectation of the desired WOT RPM, depending on which 350 setup it is. MAYBE as high as 5200.

    But I'm half-guessing--others here will know.
    "I don't have time to get into it, but he went through a lot." -Pulp Fiction

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    5000 rpm was alway my personal limit. I have seen a 35 yr old 350 sbc and volvo 270 run at 5100 for the better part of about a hour on a 70 mile one stop poker run.

    there are guys here who spin the volvo mid 5's without much issue on a daily basis . the big thing is getting the right prop so far the solas in my book is the best .

    if your motor can turn a solas 21 to 5000 you're at 60-61 mph. if your motor can turn a solas 23 to 5000 your at 67-68 mph.


    your motor will need it's wheaties to turn a solas 23 to 5000


    Sandog with the washer I would use one
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

    My Ride

    Come Join Us on The Queen Of American Lakes



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  15. #15
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    Thanks to Matty for the great description on what is needed to do to your Volvo outdrive on the prop change. I also had to custom build a plate to cover the trim fin on the lower housing. It has not seemed to impact the handling or performance of the boat. I am running the same 1972 Chris Craft conversion in my Hornet. My Chris Craft book states that it supposed to put out 320 hp. Redline is at 5600, although I have never run it that hard. To my knowledge the engine has never been torn down according to the two owners who owned it since new. It has very strong, even compression and is "dialed in" according to my standards and my marine mechanic who is quite adept and knowledgeable. Very fun to drive and enjoy!

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