Reccomend a new prop

[jfried]

Hi Everyone,

I've got a 1988 Chris Craft 225 ltd with a 350 Mag and Alpha 1 outdrive. I was hoping I could get some help decoding what size prop i currently have, and whether or not changing it would better suit my needs?

My current prop is a Quicksilver Stainless 3-blade with 48 13700 240 19p stamped on it. 19p I assume is the pitch, however I'm not sure how to tell what the diameter is?

In terms of changing it, the issue that's prompted me to consider changing the prop is twofold. First, the boat just doesn't seem to be able to drag me (270lbs) out of the water on 2 skis -- despite the fact that my 130hp sea doo can. It just doesn't plane. I also have similar issues when I've got 6 or 7 people on the boat (it's a cuddy and i'm not a huge fan of forcing the largest individuals down there). Even with tabs all the way down, it takes forever.

Running wide open with a lighter load, the tach indicates about 4200 rpms and just under 50mph on the GPS, I'm not sure what's spec for an engine of that vintage, but it seems that there may be room for improvement to get the revs closer to 5?

Any reccomendations on what I should be looking to do to improve performance? Different pitch? 4 blade prop? hydrofoil?

 

[Tail_Gunner]

Re: Reccomend a new prop

350 mags redline at 5000..at 4200 your a bit over propped..maybe. Taking it down to a 16 gets you to 4800 and a 16 is a tad small for that combo at first glance. So check the tach for accuracy would be the first step..there notorious for being off..if that is ok plug's and wires are they good last is timing how long has it been since its been timed

 

[jestor68]

Re: Reccomend a new prop

Your 1988 350 MAG's (270hp) recommended rpm range is 4200-4600 rpm.

Dropping to a 17 pitch should pick up 300-400 rpm and put you at or near your desired WOT rpm of 4600 rpm.

Solas is the best bang for the buck in aluminum props. The 4 blade provides better hole shot and mid range; good for water sports. The 3 blade provides a little more top speed. Take your pick.

 

[Tail_Gunner]

Re: Reccomend a new prop

Hmmm i need glasses the wot is 4600.. Thought i was looking at a 98 good catch Jestor...

Manufacturer: Mercruiser
Model: "350 MAG MPI Alpha-1"
Year: 1998
Horsepower: 300.0
Cylinders: 8
Type: 4 stroke
Gear Ratio: 1.47:1
Min WOT RPM: 4600
Max WOT RPM: 5000
Spline Count: 15

 

[jfried]

Re: Reccomend a new prop

350 mags redline at 5000..at 4200 your a bit over propped..maybe. Taking it down to a 16 gets you to 4800 and a 16 is a tad small for that combo at first glance. So check the tach for accuracy would be the first step..there notorious for being off..if that is ok plug's and wires are they good last is timing how long has it been since its been timed

Good point on checking the tach and timing. I don't know when the last time that was completed.

Your 1988 350 MAG's (270hp) recommended rpm range is 4200-4600 rpm.

Dropping to a 17 pitch should pick up 300-400 rpm and put you at or near your desired WOT rpm of 4600 rpm.

Solas is the best bang for the buck in aluminum props. The 4 blade provides better hole shot and mid range; good for water sports. The 3 blade provides a little more top speed. Take your pick.

If I drop to a 17 pitch, would I be looking at getting a better hole shot as well, or does that only go with the territory of a 4-blade? As I sort of mentioned, water sports is becoming an increasing priority of mine.

Is there a way to tell the diameter of the prop by the numbers stamped on it?

 

[jestor68]

Re: Reccomend a new prop

Yes; either 17 pitch (3 or 4 blade) will help the hole shot quite a bit. The 4 blade should have the edge there. The only place the "4" loses a little is in top speed(1-3mph).

Bottom line; if you want a prop specially suited to skiing, get the 4 blade.