quote:New motor after the boat gets square.
Originally posted by Fred67Whatcha doing with Herbie?
Don’t need a tree limb.
The ENTER-NET Fisherman
NOt many left around… I’ve got a dune buggy and a few spare transmissions, not much in the Junk yards anymore! Still a big following out there for them.
Ebay and this place is a decent start… https://www.partsplaceinc.com/vw-1600cc-bus-engine-long-block-1102.html?gclid=CjwKCAjwtvnbBRA5EiwAcRvnpt2sbCAN8tQCP25NzwUZNC8uLZiy_EhqNp_RnmfW2hjfK-PsFrOeeBoCTzAQAvD_BwE
These guys are a bit pricey but have complete…
quote:
Whatcha doing with Herbie?
Saw that myself. I’m an old Bug guy. I built a 2180cc with twin weber carbs. That little thing could fly. I had an original block wrapped in plastic under my house for years I’d planned to build to go into a rail buggy. Sold it to a friend and have wished I kept it.
“Apathy is the Glove into Which Evil Slips It’s Hand”, but really, who cares?
Bottom paint before I try out the motors since snappa season is over.
Egyptians gots nothing on me:
JUSSSSSSSSSt enough room
Paint one end then the other.
As an aside…the boat sits in mud for 4 hours on either side of low tide. I’'m gonna do 1 coat hard bottom black then 2-3 coats of ablative “teal” to keep up with wear. Anybody gots any better suggestions???
And I’m not done with the questions on why trimming the motor acts like a trim tab…
The ENTER-NET Fisherman
Saw this cat coming back in the other day.
mdaddy: good looking project buddy…
DG34YF: good looking cat boat buddy…
The Morris Island Lighthouse www.savethelight.org
What question do you have about trimming the motors acting like a trim tab? Maybe the confusion is coming because the trim tabs and the motor do somewhat different things to the stern of the boat?
Trimming the motor up adds downward force to that corner
Trimming the motor down removes downward force (and in extreme situations might add some lift, but not usually)
Trimming the tab down adds upward force to that corner
Trimming the tab up removed upward force (and never adds downward force)
If you think of a cat like a square board sitting on the water, just imagine what happens when you lift or push down on a corner – you get the opposite effect on the opposing (diagonal) corner. If you need to raise the stbd bow, you can trim the port motor up (to push down on that corner) or trim the port tab up (to remove some of the lift on that corner).
1994 Hewes Redfisher 18, 2004 Yamaha 150 VMAX
Malibu X-Factor Kayak
quote:
Originally posted by brysonWhat question do you have about trimming the motors acting like a trim tab? Maybe the confusion is coming because the trim tabs and the motor do somewhat different things to the stern of the boat?
Trimming the motor up adds downward force to that corner
Trimming the motor down removes downward force (and in extreme situations might add some lift, but not usually)
Trimming the tab down adds upward force to that corner
Trimming the tab up removed upward force (and never adds downward force)If you think of a cat like a square board sitting on the water, just imagine what happens when you lift or push down on a corner – you get the opposite effect on the opposing (diagonal) corner. If you need to raise the stbd bow, you can trim the port motor up (to push down on that corner) or trim the port tab up (to remove some of the lift on that corner).
1994 Hewes Redfisher 18, 2004 Yamaha 150 VMAX
Malibu X-Factor Kayak
You are a Genius…
You explained that and the light came on… I got it.
I was not grasping the force change by the change in the angle of the thrust. I wasn’t understanding WHY port trim up lifted the starboard bow…NOW I DO!!!
Thanks for the teaching.
The ENTER-NET Fisherman
Try to get a lift to keep it out of the mud! They are cheap!
Prior to Labor day, I put in some labor. 1 coat of hard bottom Sharkskin black and 2 coats of ablative Biocop in Teal so I could tell when I was wearing down…
Purchased through Amazoo…NOT!!!
Got it here:
https://www.bottompaintstore.com/boat-bottom-paint-c-13523.html
and it was delivered the next evening. I was shocked. Padded boxes and all.
The support from a guy named Tim had straight answers for my questions.
Nice paint…we’ll see how it works.
The ENTER-NET Fisherman
I like that bottom paint scheme, looks like you got a “thin blue line” thing going on. Keep us posted on the bug project, I’m an old Bug guy.
“Apathy is the Glove into Which Evil Slips It’s Hand”, but really, who cares?
quote:
Originally posted by DFreedomI like that bottom paint scheme, looks like you got a “thin blue line” thing going on. Keep us posted on the bug project, I’m an old Bug guy.
“Apathy is the Glove into Which Evil Slips It’s Hand”, but really, who cares?
I hate to be the bearer of bad news, but, that “blue” line is painters tape. I agree it’s a pretty blue.
I saw this today after reading your comment:
The ENTER-NET Fisherman
Well, it looked pretty good even though it would have been underwater.
“Apathy is the Glove into Which Evil Slips It’s Hand”, but really, who cares?
quote:
Originally posted by mdaddyThe boat weighs 5000# and has 2 150 Suzuki 150 4 stokes and made a mile to the gallon with 2 100 gal tanks. Same as with 2 strokes that are on old posts( 1998 hull) so I looks for foam being saturated…can’t find any unless it is cored somewhere(open to anyone who is alive that knows).
Checked the depth of the anti-ventilation plate and it was buried. At that time, the motors were on the lowest hole setting…upper and lower bolts( no open channel on the bottom like Yamahas{stronger design but a PIA???} The last good tree limb I have left on my yard after the last herd a cane, required a 4x4 as backup and motors were raised 2 holes…probably should have gone 3… we’ll see.
The hardest part was removing the inspection plate covers in the stern pods…some kind of sealent that required some prying…idiot that did it. Presently about an inch above the bottom of the transoms…we’ll see.
THe reason for the lengthy post is, by raising the motors, will I lose any noticeable abilty to trim the motors that is obviously required to control the boat??? We’ll see.
As always, I wouldn’t axe on a public forum if I was talking to myself.
And Skinny, glad to see you posting and I know you gots a cat…and you never been short on opinion.
Also swapped the drives to have the counter rotator on the starboard side so the props turn toward each othe and give more combined thrust.
Stern lift is mentioned as a positive ie. changing to 4 blade props. Presently running 3x15 1/2x 17 with rpm of 6k at full load so it is propped correctly…FOR THE LOWEST motor setting. I would imagine the rpms will increase after raising the motors 2 notches…we’ll see.
I need this boat to make at least 1.5 mpgs or better to make the amazing ride worthwile. We’ll see.
The ENTER-NET Fisherman
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unless that is a typo, you’re going the wrong direction on your prop choice to decrease rpm. Increasing diameter will have an effect on rpm and speed, but stepping back on the pitch will negate any gains
quote:
Originally posted by sparepartsunless that is a typo, you’re going the wrong direction on your prop choice to decrease rpm. Increasing diameter will have an effect on rpm and speed, but stepping back on the pitch will negate any gains
"The addition of the extra blade causes increased drag, which, in turn, requires more horsepower, to achieve the same rpm. Since the horsepower is limited, the RPMs drop, and the speed will tend to drop with it. Therefore, when going from a 3-blade to a 4-blade, the pitch is dropped an inch or two in order to keep rpm parity. It is this difference in pitch that causes any potential speed differential between the 3-blade and the 4.
As to any actual speed loss between the two, in many cases, it is quite small (generally 1-3 mph). The reason is, although the 4-blade is one-inch lower in pitch, it runs more efficiently than its 3-blade competitor, allowing it to run closer to its theoretical speed than the 3-blade, thereby, effectively closing the gap presented by the pitch differential."
https://www.getaprop.com/powertech,%20propellers,%20outboard,%20boat,%203,%204,%20blade
The ENTER-NET Fisherman
I have to agree with spare parts.
dropping from a 17 to a 15 pitch, even though you increased diameter and blade count, is most likely not going to increase your cruise rpm, and decrease your cruise speed.
as for the speed change being “quite small”…
3 mph, thats a 10% reduction.
thats substantial when calculating long term fuel burn.
In my experience, is EXTREMELY rare that going to a 4 blade prop improves anything except stern lift. that being said, boats that are very stern heavy, and need teh additional lift, will then get better top end, and better fuel economy, but like i said, its rare.
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
quote:
Originally posted by chris VI have to agree with spare parts.
dropping from a 17 to a 15 pitch, even though you increased diameter and blade count, is most likely not going to increase your cruise rpm, and decrease your cruise speed.
as for the speed change being “quite small”…
3 mph, thats a 10% reduction.
thats substantial when calculating long term fuel burn.In my experience, is EXTREMELY rare that going to a 4 blade prop improves anything except stern lift. that being said, boats that are very stern heavy, and need teh additional lift, will then get better top end, and better fuel economy, but like i said, its rare.
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
All I can go by is what the peeps that make the prop say.
This cat hull is a planning catamaran hull versus the World Cat/Glacier Bay displacement hull.
5K-6K is top end propping RPMS
With the 15 1/2 diameter 17 pitch props:
29 kts at 6K rpm
20 kts at 4100 rpm
after raising motors 2 mounting holes
These numbers were best with the TRIM TABS BURIED and motors trimmed all the way down???
This goes against everything on a V hull boat ie.
Usually as the bow raises on a v hull boat speed increases due to less surface area in contact with the water at planning speed…and as you trim up the motor the speed increases until prop breaks loose.
Not in the case with this boat.
I’m not looking for speed…best crusing fuel economy is what I would like. I would suggest that the 4 blade props WILL GIVE MORE STERN LIFT…WHICH is what I’m doing now by runnig with the tabs down.
I will dial this in…just seems a$$ backwards.
The ENTER-NET Fisherman
let me guess, powertech???
we have had several issues with props they have recommended, performing poorly.
The last time, was involving a 20’ pathfinder.
the recommended prop was 10mph slower, yes, i said 10mph slower than what we ended up with based on another boat setup with the same motor.
I know you say you arent looking for speed, but higher top end, equates to higher cruise speed at any given RPM, which equals better fuel economy.
Also, any of the Mercury props are VERY good props, and thats coming from a diehard Yamaha guy.
its a planing hull, correct?
if its a planing hull, the more hull you get out of the water, the faster it runs.
now, it could be so stern heavy that you get more hull out of the water by lifting the stern. that said, you will reach a point where the stern lift maxes out, and it then starts to bury the bow, and your speed will decrease.
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
quote:
Originally posted by chris Vlet me guess, powertech???
we have had several issues with props they have recommended, performing poorly.
The last time, was involving a 20’ pathfinder.
the recommended prop was 10mph slower, yes, i said 10mph slower than what we ended up with based on another boat setup with the same motor.
I know you say you arent looking for speed, but higher top end, equates to higher cruise speed at any given RPM, which equals better fuel economy.
Also, any of the Mercury props are VERY good props, and thats coming from a diehard Yamaha guy.its a planing hull, correct?
if its a planing hull, the more hull you get out of the water, the faster it runs.
now, it could be so stern heavy that you get more hull out of the water by lifting the stern. that said, you will reach a point where the stern lift maxes out, and it then starts to bury the bow, and your speed will decrease.www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
Carnac the Magnificent…great guess.
Between you and Spareparts…we can figure this out.
The 3 blade 15 1/2" diameter by 17 pitch props turn the prop range at 6000rpm(with tabs buried/motors trimmed down)(5000-6000rpm for 150 Suzuki 4 stroke with 2.5/1 gear ratio)
If I went with 4 blade 16" diameter by 17 pitch props,
I should see a drop in rpms by 250rpm( 1" diameter bigger drops rpm by 500 so 1/2 increase should roughly drop by 1/2) AWA a drop of about 200 rpm by maintain the 17" pitch. Roughly being off 500 rpm of the 6000 rpm I’m turning now with full fuel/tabs buried/ and no up trim on the engines.
Keeping the pitch the same ??? another 200 rpm loss roughly???
Chris(Carnac)I see your point about speed across all rpm ranges as the motor will be mor