Prop selection for Maxum 1900SC

I have an oddity of a boat, it's a 2000 Maxum 1900SC Cuddy with a 80's volvo AQ131a and 275 Drive.
My stock aluminum 3 blade 14x17 has been slowly losing speed this season, seems like I'm spinning more rpm to go the same speed. Not alot but enough to notice like 1 to 1-1/2 knots. Slip is awful, calculated at 29%.

My specs are:
19' long Cuddy cabin boat, 15* semi deep-vee hull.
Stepped transom(swim platform is molded in)
130HP 4-cylinder AQ131a OHC I/O
~3500#'s fully loaded with people gear and full fuel
I cruise at 4500rpm seeing 21kts, and WOT at 26-28kts depending on conditions at 5350 rpm.
Getting 4.2mpg.
I have 60# smart tabs set on hole #5. Hole 4 and 5 work great, hole 3, and the boat starts to porpoise a little bit.
My drive ratio is 2.15
I have a 9.8HP kicker on the back(reason for the tabs-weight hurt performance and getting on step). It planes easily with them, I'm up in about 5 seconds.

I'm looking for a few more knots at cruise, and to wot at around 5000rpm. A VP 14x19 3-blade leaves me 200rpm short of wot spec. I want to stay with aluminum props to protect my drive. I've seen several change to the solas amita 4-blade and see better results all around. Is a 14x17 4-blade going to be the ticket?

Re: Prop selection for Maxum 1900SC

Its Highly unlikely your prop is losing speed.I would suspect the bottom and possibly the prop or fouled with growth of some sort.Agressive use of tabs will lower speed and may increase slip.If your prop is old and worn it could have high slip numbers.
A 17" 4 blade will reduce your rpm some especially considering your present slip numbers, and improve hole shot and ability to stay on plane at reduced throttle may allow easing up the tabs.It will surely improve your slip numbers.The Solas amita is effective and reasonable.

Re: Prop selection for Maxum 1900SC

My boat is trailered so the bottom is kept nice and clean as well as the drive.
I did run into a wad of kelp awhile back, and it got all wound up in the prop and we had to raise the drive and clear it. It lost a little after that, but since then has lost probably that much again. I suspect maybe increased cavitation due to wear and maybe it's tweaked just a touch from the kelp tangle.....
I was thinking the same thing, that I could try the 4-blade and back off the settings on the smart tabs.
I was hoping HSWiii would get in here with all his experience and prop charts and verify before I buy...no one carries much for VP props locally so I need to try to get it down to a couple "best shots" order them online, and go from there.

Re: Prop selection for Maxum 1900SC

hwsiii often suggests the solas amita 4 and it does usually perform as predicted.
They have been very effective.
Stick to a diameter about the same as your present prop avoiding excessively large diameter.You could try pm ing H.

Re: Prop selection for Maxum 1900SC

19 pitch solas amita 3 blade would benfit you the most...17p 4 blade would keep the rpm up and the mph down. You have trim tabs assisting your launch..And the 19 should keep that old four banger about 4700-4800 good place for those old girls...

Re: Prop selection for Maxum 1900SC

I could give it a try, I've also got a new VP 14x21 that I'll never spin that I got for $45 off ebay. It's actually the same pitch as the 14x19 but the blades have more "duration", I was thinking about reshaping the blades to be just a touch smaller than the 14x19 and see how it does.
I'd really like to spin my volvo about 5000 wot or more. I actually have all the parts and will be building a head with twin carbs to upgrade me essentially to the AQ145, the cam and twin sidedrafts being the key to another 20HP but also recommended to wot at 5000-5500rpm.

With the kicker motor and twin batt's I feel I'm pretty stern heavy, which is why I am kicking around the 4-blade idea. I noticed that when I had my 100# wife on board, the boat would lose almost a knot when she went to the stern to get something, then speed up again as she came forward.
I realize my power is marginal, but its really nice to get the economy that I get...even at $3/gallon three of us can go fish all day and split a $35 gas bill!

Re: Prop selection for Maxum 1900SC

17 @ 5200prm @32 mph nets 21% slip. Not that bad if your running around with a full load of people and gear i think. Do you have any numbers running empty with no people to see how the boats runs by itself

Doing a 17p 4 blade will or should lower your slip and at that speed the drag of the 4th balde might not have a negative impact on top speed..Now doing a 19 puts you at 41mph about right for that motor and boat..with 1 or two people

Re: Prop selection for Maxum 1900SC

Tail_Gunner said:

17 @ 5200prm @32 mph nets 21% slip. Not that bad if your running around with a full load of people and gear i think. Do you have any numbers running empty with no people to see how the boats runs by itself

Doing a 17p 4 blade will or should lower your slip and at that speed the drag of the 4th balde might not have a negative impact on top speed..Now doing a 19 puts you at 41mph about right for that motor and boat..with 1 or two people

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I test run on a local lake often by myself, and usually see 5350-5400 rpm at wot. It had been over 5500 rpm wot before I mounted the 9.8.
The 3 blade 14x19 I thought I would be able to pull, but when I loaded up 3 people full fuel tanks kicker and downriggers it didn't happen. Fell short around 4700 and the motor didn't seem to like it....sounded too heavily loaded, I had the 17 pitch on board so I swapped it out.
The numbers were 23.5 kts at ~4200 rpm with the VP 14x19, wot speed didn't really increase though only about 28kts. The cruise speed I liked but I was wishing I could just get ~200 rpm more so I could run that one.
Aside from a shorter pop up time I don't notice that much difference between just me and 3 people relating to cruise speed and wot rpm, although top speed definately suffers with more load.
The motor runs good, in the original boat(1986 Capri B/R 19') it pulled the next size prop over what the manual stated when fully loaded.

What would I see from the Solas 14.8x17(basically a 15x17) three blade?
Unless it's not going to be hardly any difference I'm thinking of getting it and the 4-blade 14x17.

Re: Prop selection for Maxum 1900SC

rkcarguy said:

I test run on a local lake often by myself, and usually see 5350-5400 rpm at wot. It had been over 5500 rpm wot before I mounted the 9.8.
The 3 blade 14x19 I thought I would be able to pull, but when I loaded up 3 people full fuel tanks kicker and downriggers it didn't happen. Fell short around 4700 and the motor didn't seem to like it....sounded too heavily loaded, I had the 17 pitch on board so I swapped it out.
The numbers were 23.5 kts at ~4200 rpm with the VP 14x19, wot speed didn't really increase though only about 28kts. The cruise speed I liked but I was wishing I could just get ~200 rpm more so I could run that one.
Aside from a shorter pop up time I don't notice that much difference between just me and 3 people relating to cruise speed and wot rpm, although top speed definately suffers with more load.
The motor runs good, in the original boat(1986 Capri B/R 19') it pulled the next size prop over what the manual stated when fully loaded.

What would I see from the Solas 14.8x17(basically a 15x17) three blade?
Unless it's not going to be hardly any difference I'm thinking of getting it and the 4-blade 14x17.

Click to expand...

Propping the boat for a full load and trying to get the lowest slip possible and still be @ wot is good planning. I doubt you will see any speed gains but a better hole shot...and more midrange punch and keeping the motor from lugging is the benefit..19' boat 1000lbs of weight 30 mph plus is quite good for a 4cly engine..You are right in looking for a 17p 4 blade and solas props are quite good.

I dont think a 18 would be of any benefit and i dont believe they make one ...thats solas

Re: Prop selection for Maxum 1900SC

Tail_Gunner said:

19' boat 1000lbs of weight 30 mph plus is quite good for a 4cly engine..

Click to expand...

I was surprised myself that it did that well, I had nearly purchased a 4.3L to swap in before I even tried it. I'll pull the trigger on the 4-blade 17 pitch and report back....probably in late March

Re: Prop selection for Maxum 1900SC

Update:
I installed the 4-blade Solas Amita 14.5x17 and noticed a good increase in holeshot and cruise speed. It took maybe a second off my time-to-plane, and now cruises 24.2 knots at 4500 rpm.
Wot rpm was ~4800, I would have liked to be a bit higher. It only gains a couple knots from 4500-4800, I haven't tried it with more people so it's hard to say if it will pull the extra load and stay within spec of 4800-5000 @ wot.
I can also note the prop is much smoother than any of my 3-blades.
If nothing else, I am preparing a new cylinder head with some upgraded goodies in it that should yield another 20HP so it should pull this prop. Overall I'm pleased, 4-cyl volvo guys just need to be aware that the same size and pitch prop going from 3-4 blade will drop the wot RPM ~500rpm lower.

Re: Prop selection for Maxum 1900SC

You can easily drop an inch in pitch when empty, add people and take another inch off. If you'll be taking people more often than knot, go with 2" reduction and watch your RPM when "empty".

Good deal!