Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Big-E · Feb 25, 2006

Hey guys, I have posted a couple of times about prop advice for my 16.5 foot bowrider. Rebuilt my motor last year and this thing runs great. Spun the old worn out prop and per advice from the prop shop bought a brand new black max 15 x 19. The old worn out prop was a 14 x 23 but was in bad shape. It would only allow her to spin up to 4100 rpms at 38 mph gps (found log i made) This 15 x 19 is way to small for average cruising but will make a great water toy prop. Man she pulls like a tractor up to 35 mph but thats it. Im looking for a prop that will keep me in the upper end of max rpms. My boat weights around 2200 lbs fully loaded. Think she should beable to twist a 14 x 23 back max? I was thinking of getting a 14 x 21 since thats what most newer boats run but they are a full foot longer then mine. I just dont want to buy props that i wont need.. I'll be buying them used since i have a couple of boat bone yards near me but they will not let me try one out 1st. So my real question is for those who have boats in 16-17 foot range what size props are u running? Thanks, Big-E

Bondo · Feb 27, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

You Don't say what your RPMs are at WOT with the 19".......... The 23" is Too Big...... The 21" Might be the 1......

Big-E · Feb 28, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

I knew i forgot to include something.. Thanks Bondo.. WOT with 19" is unknow.. It will pull past 5000 rpms w ease. Last time i had her out it hit 5000 rpms and had room to go. It also got there way too quick.. So quick i was at 5000 before i even trimmed the boat out. Motor is 3.0 Inline 4 cyl. RPM range 4400-4800 rpms. Id like her to be propped around 4800. I didnt keep her at 5000 for more then a sec but it wanted to climb fast. SO my post should read.. Those with 3.0 L's and 17 foot boats what size prop do you run? Thanks, Big-E

tommays · Feb 28, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

I am bigger at 19.5 and run a vented 19" which if i am alone is on the small side but just right with 3 to 6 people. I could spin a 21 BUT the hole shot will really suffer and i might only pick up 1 or 2 MPH on the top speed which is 41 MPH with the 19" The 3.0 does really not have enough low end punch to spin big props out of the hole like a V-6 or V-8 so you have to make more compromises to get a good all around prop. tommays

Big-E · Mar 2, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Thanks for the replys guys!!! I just put a pond in my backyard this past weekend so im going out to the local lake to get some plants for it. I will be running the boat and let her streach her legs for the 2 months she's been on the trailer. Im thinking the 21" might be the way to go.. Good thing about this 19" prop is it pulls like crazy!!! thanks, Big-E

Tail_Gunner · Mar 2, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

I have a 17 foot 3.0 with a 2.1 final gear ratio. What i was finlly able to come up with was a 20" 4 blade for water sports and a 22" stainless for cruising. One of the things that i am going to do is vent the stainless starting with 1/8" vents and work it up from there, there is something to be said for a quick up and otta there hole shot..........................

.....

I might just have to vent that 4 blade.............

Big-E · Mar 3, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Tail_Gunner: What max rpm are u at with the 22" SS ? I dunno if anyone can answer this but i heard that with a 23" prop and 2.0 final gear ratio you rpms are the same as mph.. ie. 30 mph = 3000 rpms. Any truth in this? Thanks, Big-E

walleyehed · Mar 3, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

It can only be the same if the slip ratio is the same....one thing for sure, it's never the same on 2 different boats.

vipzach · Mar 3, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

I have a 17.5' boat, I am currently running a 17" SS rapture prop. It jumps out of the hole an onto plane very quickly and tops out around 38 mph at about 4600 rpm. This summer I am going to put a 19" prop(don'y know what brand yet) and smart tabs on and see if I can still get a good hole shot and a little more top end.

walleyehed · Mar 3, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

The smart tabs with the 19 will give a better hole-shot than the 17 ever did...question is..will you still be near the top of your RPM range with the 19??

vipzach · Mar 4, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Originally posted by walleyehed: The smart tabs with the 19 will give a better hole-shot than the 17 ever did...question is..will you still be near the top of your RPM range with the 19??

I hope so! Do you think it will put me way under? I know, it is trial and error and I will probly just have to chance it. Do you have a better suggestion?

--GQ-- · Mar 4, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Big Easy, I have an 18 footer. 4 cycl. 4400-4800 rpm range. I have 3 props; 3 blades alu. 21p, 3 blades SS 21p, and a 4 blades composite. I am currently using a 4 blades adjustible composite prop adjusted to 22 p. Good holeshot. Max speed at 43mph at 4400 rpm. The SS, i got 45mph but poor holeshot.

walleyehed · Mar 5, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

vipzach, you'll just have to give it a test run to see... Remember, you want the top of the range with a NORMAL load...

vipzach · Mar 5, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Originally posted by walleyehed: vipzach, you'll just have to give it a test run to see... Remember, you want the top of the range with a NORMAL load...

I know I will just have to give it a try, I know a guy that owns a prop shop, I am hoping he will let me try out a couple before I buy one. Any suggestions on a brand? Big-E, sorry about jacking your thread here, our questions are kinda along the same lines, so I thought maybe it might help you also!

Tail_Gunner · Mar 6, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

I have tried running a #18 prop and well i did get a nice hole shot i was running @ 5100-5300 rpm(not sure) @ wot. For my self i felt that was a tad high for a 3.0 pushrod 4 cyl. What i aimed for was a 4800 rpm wot and the best hole shot, that gave me a 20" 4 blade and a 22" stainless. Although your motor is a older version than mine i believe your running the rpm a tad slow. This can be a highly opinionated topic (rpm) but i would take the time to see if your tach is really accurate. Doing a sharp turn does the boat cavitate @ all? Running a older 4 cyl thats carbed and they run a little cool might not get one the best economy and lug the motor a bit (not good) 4400 rpm?

For my self i have taken a direction at which rpm does the motor run at the peak of its operation range, and how fast do i get out of the hole. For now max speed is not a concern

as i have some kind of cupping on my transom that i believe the mfg built in, which makes me want to name this boat Bronco....

Big-E · Mar 7, 2006

Re: Prop question for those with 3.0 L alpha 1's and boats under 18 feet

vipzach : Dont worry, your question is the same as mine. I had my boat on the lake this weekend just to let her run and got some more data on my 19" prop. I never took her over 4800 rpms but she had lots to go. I gota say my motor really sings above 4500 rpms.. It sounds really good and she seemed very happy up there. I didnt run it as long as i wanted since my u-joints were sounding like they wanted to explode. (ive known they were bad since the end of last season. Have to change them out this weekend) If i punch it at 3000 rpms it takes off like my old 400 hp turbocharged 300zx. Scared my 250 lb brother-in-law that was sitting up in the bow. Its a pretty cool feeling even with 3 adults int he boat. Later, Big-E

Prop question for those with 3.0 L alpha 1's and boats under 18 feet

Petty Officer 2nd Class

Moderator

Petty Officer 2nd Class

Admiral

Petty Officer 2nd Class

Admiral

Petty Officer 2nd Class

Admiral

Lieutenant

Admiral

Lieutenant

Chief Petty Officer

Admiral

Lieutenant

Admiral

Petty Officer 2nd Class