Prop recommendation

4js · Jun 1, 2011

I have a 19 ft maxum 1900sr with a 3.0lx and alpha one gen two drive.
Typical load with all people gear and cooler is about 800 pounds.

I have a Mercruiser Vengeance 3 blade 17 pitch stainless prop
I hit 4800 rpms at about 75% throttle. I have not taken the throttle all the way down to see what max rpms would be

Been doing some looking and reading and I think I need at least a 19 pitch.

Based on info provided would you agree?

CobiaXL · Jun 1, 2011

Re: Prop recommendation

yep or maybe 21 with light load

4js · Jun 1, 2011

Re: Prop recommendation

Thanks for the reply. Does anyone have any recommendation on the type and brand that I should look for? I would like a stainless steel but other than that I do not know much

Robbabob · Jun 2, 2011

Re: Prop recommendation

Don't know that you'll see much benefit with a SS. Heavier boats with high HP see it better. Save the $$$ and stick with AL.

my $.02

4js · Jun 4, 2011

Re: Prop recommendation

That makes sense...so would this be a good fit for my application? Is this a good prop?
http://boatpropellers.iboats.com/Me...ith_Flo-Torq_Hub_QA1916X_Propeller/437/19586/

hidef · Jun 4, 2011

Re: Prop recommendation

Not knowing the history of the boat did you buy it used or new and is that the prop that came on it? If it is I would open it up to make sure what you max revs are before I would start spending money on props. Remember adding two inches of pitch will drop your RPMs by 300 if you stick with stainless. If you go to a 19" AL you will see no difference in RPMs due to the increased prop slippage you would need a 21" to see an impact. Also as you increase prop size your boat will be slower coming out of the hole not good if you are pulling are skiers.

4js · Jun 4, 2011

Re: Prop recommendation

If you go to a 19" AL you will see no difference in RPMs due to the increased prop slippage you would need a 21" to see an impact.

This contradicts what Robbabob said....3.0Lx is not big enough to have an impact on an AL prop. ?

I bought the boat used, but the prop on it is not the original prop. 17p on this boat/engine doesn't seem to match up with anything I've read.

And finally - with the current prop I have, max RPM would be around 5300 give or take...I was at 4900 last night and still had room to go, but didn't.

Robbabob · Jun 4, 2011

Re: Prop recommendation

4js said:
If you go to a 19" AL you will see no difference in RPMs due to the increased prop slippage you would need a 21" to see an impact.

This contradicts what Robbabob said....3.0Lx is not big enough to have an impact on an AL prop. ?

I bought the boat used, but the prop on it is not the original prop. 17p on this boat/engine doesn't seem to match up with anything I've read.

And finally - with the current prop I have, max RPM would be around 5300 give or take...I was at 4900 last night and still had room to go, but didn't.

Sorry for the confusion! I must have thought you currently had an AL prop asking to go to a SS prop. Now that I've read your original post, I realize my mistake. There will usually be more slippage with an AL prop, yes, but in some cases it's not actually worth the money to go with SS. it's all up to you.

You do need to go up in Pitch to reduce your rpm, but know that your hole-shot will be less effective. If you are more into water sports and don't mind giving up the top speed worrying about max rpm, go with the 19P. If you want more of an all-around prop trying to satisfy all variables, then the 21P may be your best choice. As already stated, you may want to see where your rpm will get to for a short time just to know how many inches of Pitch increase you need.

Tail_Gunner · Jun 4, 2011

Re: Prop recommendation

4js said:
I have a 19 ft maxum 1900sr with a 3.0lx and alpha one gen two drive.
Typical load with all people gear and cooler is about 800 pounds.

I have a Mercruiser Vengeance 3 blade 17 pitch stainless prop
I hit 4800 rpms at about 75% throttle. I have not taken the throttle all the way down to see what max rpms would be

Been doing some looking and reading and I think I need at least a 19 pitch.

Based on info provided would you agree?

Vengance is a pretty grabby prop..are your getting good performace speed now??? If you could post your mph taken with gps it would help quite a bit...i take the numbers you have posted was with a full load of people...and if so i think your dead on in a prop.

Now as to the last little bit of throttle...there is not much there or should not be much there. Boats have cams that run out of breath at about 45-600 rpm so do this if you can...Nail it for a 30 second burst and see if you can climb to 5000 rpm you might be surprised to hear more noise and thats about it.

4js · Jun 4, 2011

Re: Prop recommendation

Thanks for the responses! With a full load of people on the current prop the gps reads 26-27 mph at 3800 rpm. Thats my typical cruising speed. At 4600 rpm I'm running at 30-31.
We do not ski, just tube the boys around. What I'd like to have is a little more speed when cruising in the 3600-3800,rpm range. Not really worried about quick hole shot as much as mid and top range speed at correct rpm
Does this help any?

4js · Jun 5, 2011

Re: Prop recommendation

Max speed on this boat w/the correct set up should be around 45, right?

Tail_Gunner · Jun 5, 2011

Re: Prop recommendation

4js said:
Max speed on this boat w/the correct set up should be around 45, right?

45 might be a the ragged edge for a 19' with a 3.0 maxxum nice boats..On your outdrive there is a stamped number 1.89 2.0 could you post that... When you say loaded is that 4, 6 or 8 people adults kids overall all weight is what im looking for...You may want to check your plugs and timing on the engine.. 4cyls are very easy to work with.

I think your at the boats peak now.. if your running 6 people...and turning 4600 rpm that 3.0 is really working

4js · Jun 5, 2011

Re: Prop recommendation

When I say loaded...that is 5 people and cooler...around 800 pounds.

The only thing I found on the outdrive was "1.94 R". Does that help?

The spark plugs are new and timing is good. Engine runs like a champ.

So....are you saying going to a 19p vs the current 17p wouldn't help lower RPM AND give more mid and top end speed?

Tail_Gunner · Jun 5, 2011

Re: Prop recommendation

4js said:
When I say loaded...that is 5 people and cooler...around 800 pounds.

The only thing I found on the outdrive was "1.94 R". Does that help?

The spark plugs are new and timing is good. Engine runs like a champ.

So....are you saying going to a 19p vs the current 17p wouldn't help lower RPM AND give more mid and top end speed?

Lets try to get on the same page... With a boat loaded to 800 to 900 lbs 18' in length probably a 2500 lb boat by itself...total of 3400 lbs using a 120 horse 4 cyl doing 31 mph @ 4600 with a 1.94 gear ratio get a slip of 18% thats pretty good.

Empty just you using a 19p would get you somwhere around 43 mph thats 11% slip and quite fast for that boat...

I believe your propped quite well for a load actually perfect for a boat load of people and dont see how you could change the speed....Now you could put a 4 blade 17 pitch alum say solas.That should give you more midrange and just a bit more rpm at a speed loss of a 1-2 mph...Big thing here is performance characteristic change....smoother...more midrange punch

Having two props for a boat is not at all unusal...one for light loads and one for heavy loads...Personally i have a 22 for high speed play....20 for all around boating and a 18 if the kids are going out with there freinds....Hmm maybe in need a pontoon boat.. but propping for the load and application is much cheaper

.

Bamaman1 · Jun 5, 2011

Re: Prop recommendation

I think a 19 pitch prop would better suit you, and give you a little more top end.

I switched over to stainless propellers for the durability. I'm on a rock bottom lake, and was invariably going through a prop repair per year with an aluminum propeller. When I switched over to a stainless prop, I never dented or scratched the prop in 12 years. A stainless prop is 3x higher, but actually a better value in the long run.

4js · Jun 6, 2011

Re: Prop recommendation

Ok, I opened it up tonight for 30 seconds or so, went up to 5600 rpm, gps said 40.2 mph. Does this help any? Still think I need a 19p prop....

4js · Jun 7, 2011

Re: Prop recommendation

This added info didn't help at all?

Tail_Gunner · Jun 7, 2011

Re: Prop recommendation

4js said:
Ok, I opened it up tonight for 30 seconds or so, went up to 5600 rpm, gps said 40.2 mph. Does this help any? Still think I need a 19p prop....

Well that changed the story

5600 with a 17p ss
5400 with a 18
5200 with a 19
5000 with a 20
4800 with a 21

I believe you were right all along with the 19 if you intend to run with people

17p... 5600 rpm....1.94 gears....40 mph gets 13% slip which is good. It is obvious there was a lot left of that last 1/4 throttle good thing you checked..Stilleto make a very good 3 blade ss in a 19 as does Solas....Either prop should wake up your boat nicely...The Stilleto should drop the rpm level a bit lots of cupping oh that prop and overall lift

http://boatpropellers.iboats.com/Me...19.00-Pitch_Propellers/437/?rotation=Standard

4js · Jun 8, 2011

Re: Prop recommendation

Thanks a lot for that info. Any suggestions on a good aluminum prop?

americaneagler77 · Jun 29, 2011

Re: Prop recommendation

solas amita 3 or 4

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