does this prop seem "reasonable" for this combination?

[ScottinAZ]

not trying to fix an issue per se, but see if what I have is "reasonable" given the combination that I have.

Boat is a 1980 vintage 16' vhull bowrider with a Mercruiser 120 engine, MC-1 drive (1.98 ratio?) prop that is on the boat is unmarked in any way that I can find (nothing under the mount nut, nothing I can see stamped on the outside). Gets up and moves good (IMHO) and tops out between 43-4600 rpm. I do not currently have a speedo on the boat.

The boat came with a couple of "spare" props, one of which was used to break rocks, but is marked as a 17 pitch (didnt bother to run all the numbers, it needs to become beer cans again) the other is a very good condition Michigan Wheel 031024 which works out to a 14.5x17. Since the current on the boat is unmarked, and this one could just have been tossed in the boat at random, does a 14.5x17 seem appropriate for the combo? Not looking for full on barn burner performance, but having a good spare on the shelf is not a bad thing..... if this prop is appropriate(ish)

 

[Scott06]

I would think a 17 or 19 would work with that application. Quite possible a 17 works well Especially if its a fiber glass boat ( heavier than aluminum). If i recall my neighbors growing up had a 17” on their startcraft bowrider that had a 120.

You could have the pitch verified by taking it to a prop shop

 

[ScottinAZ]

I would think a 17 or 19 would work with that application. Quite possible a 17 works well Especially if its a fiber glass boat ( heavier than aluminum). If i recall my neighbors growing up had a 17” on their startcraft bowrider that had a 120.

You could have the pitch verified by taking it to a prop shop

its fiberglass. good to know a 17 isnt out in left field somewhere...... as for the existing prop, well, if I were to take it to a prop shop, the least of their concerns would be the pitch...... its shall we say a bit "rough" around the edges.... Methinks the previous owner either liked to make small rocks from large ones with his prop, or fished in some damn shallow waters (bottom of the hull was clean and no major scratches, for being 42 years old....) and didnt know how to trim up

 

[Texasmark]

Using your RPM upper engine spec as a limit, toss it on and see what happens. If it works good unless you are alone and it wants to over rev., you know where the throttle control is located. Grin

 

[ScottinAZ]

I popped on the Michigan prop. We will see what it does. Either I won’t notice a difference, or we just piddlefart around the lake as usual. We don’t usually go for top speed, just out to burn gas, **** off the environmentalists and have some fun…..

 

[airshot]

Your tach tells the story, looke like you are right in your range but mabey a little high. On my boats, I prop to max rpm with the lightest load I ever plan on running, in other words, just me and minimum gear. Adjust pitch to give max wot rpm. Then I will be good with passengers etc. If towing toys or heavy loads, I carry a spare prop with two inches less pitch, easy to change if needed. Always important to watch that tach when ever your running near wot !!

 

[ScottinAZ]

Your tach tells the story, looke like you are right in your range but mabey a little high. On my boats, I prop to max rpm with the lightest load I ever plan on running, in other words, just me and minimum gear. Adjust pitch to give max wot rpm. Then I will be good with passengers etc. If towing toys or heavy loads, I carry a spare prop with two inches less pitch, easy to change if needed. Always important to watch that tach when ever your running near wot !!

Ill have it out on the water again likely tomorrow. The props all came with the boat, and now I have the best of the three on there. One is scrap, another is serviceable, but could use some love with a file (and a rebalance after) to knock off the burrs, and the one on there now has a couple small dings, but is in near perfect shape. From looking at them, two are Merc props and one is a Michigan. all appear to be a 17 pitch at between 14.5 and 15 inch diameter. I finally found the numbers under a bunch of crap in the hub on the last prop......

 

[ScottinAZ]

Using your RPM upper engine spec as a limit, toss it on and see what happens. If it works good unless you are alone and it wants to over rev., you know where the throttle control is located. Grin

well, this is what we did today...... worked great, right up until the hub spun...... well, so much for that... time to find a prop shop to rehub the damn thing now.....