Time to plane

NRath

Captain newbie here...  I've taken one trip, the sea trial, in my Captiva 192 4.3GXi, stock prop (14.5 x 19º, I think).  I had read a review about it and it said time to plane was like 3.8 seconds.  Having been boating a fair amount (with other people), I knew that was pretty quick.  However, my girl is timed at more like 8-9 seconds.  With a couple people in back- wouldn't do it.  Move some weight up front and it'll plane.  3 people on board- speedo hits 49 mph.  Compression checked out good on all cylinders and it seems to run like a top so far.  What gives?

Also, the reviewed boat was a Merc 4.3 non-fi, so it should have only been 190 hp, vs my 225...

Should I try again with no other passengers?  Of course, a prop change or trim tabs would help.  Just puzzled and a little concerned why the reviewed boat would be so different.

mvn

Yes,  weight makes a huge difference on the 192.  A 19" prop should be perfect.   Smart tabs also make a huge difference.   The boat pops out of the water with them on. 

What is your wide open throttle rpm? 

Mark 

MarkB

For sure weight at the back is going to have a negative impact.

Read conditions of the test, they should specify tank level, number of people on board, etc.  I'd imagine at 3.8 seconds they basically had 1/4 tank of fuel and only the boat operator on board, perfect water conditions (flat water), etc.

Do you have smart tabs? That will make a big difference.

nhsd

did you have the outdrive trimmed down? even with several people in the back that boat should be able to plane and relatively easily at that. trim all the way down, give it the gas, get on plane then trim up for speed. Sorry if you already knew and did that, but as a newbie I wasnt sure... my 212 with 220 HP and 21 pitch props planes very easily when trimmed properly.

NRath

Nhsd- that's exactly how I launched.

As for test conditions, I didn't see that in the article.  I was def worst case w/2 passengers and a full tank of gas, though.

My boat is all stock, as I assume the one in the review was.

Good comments, keep them coming!  I hope to get out tomorrow evening for an hour or so.

Michael T

I had a 2006 192 with the Mercury 4.3 LX. It was fast with gas and just the Admiral and I but slowed quickly under load. I definitely had to move people forward if I wanted to plane faster with food, drinks and gear on board. Your 4.3L is a great engine though as a six cylinder engine is inherently balanced and Mercury (and Volvo) added a harmonic balancer to those engines for extra smoothness. I think my prop was 19" too but can't be sure, easy to check your prop though, just go out with the Admiral and 3/4 or so tank of gas and normal gear you should fall in the upper end of the rpm band. As I think of it 19" does sound right for o.e.m. as a 21" pitch would probably be too tall. I think my gearing was 1.81

NRath

Thanks MT, good for some confidence in what I bought.  While shopping, I decided a 4.3 FI is what I thought would be a happy middle ground between fuel economy and horsepower.  I made a run a couple days ago- surprisingly 3500 rpm at 47 mph on speedo.  I have a gps to verify with now, but the boat was too loaded today to worry about it.  I did see the speedo reads about right from 25-30.  So, if those numbers turn out right, there's room for a prop change that should be very helpful.

NRath

So, I hit the water with gps in hand.  I hit 49.3 top speed, wot, at 3600 rpm.  Clearly, the rpm should be up at 44-4800, indicating a prop pitch issue to me when combined with the slow holeshot times.  A different article I read (Boattest, I think this one was) has the boat hitting 49 mph @ 5000.  Guess it wasn't their boat so they weren't worried about overrev.  But, it's still relevant.  Same article also said it cruised 24.8 mph at 3000.  At 24.6, I was at 2100.  The speedo is pretty accurate- +- 1/2 mph.

Interestingly and unrelated, I hit about the same top speed w/3 people and a full tank vs 2 people and an empty tank.  Empty?  yes, because then I ran out of gas.  lol.  I had 3/8 tank when a left the dock!  So, my first time fueling came thanks to a friendly lake front owner.  I like new friends...

Handymans342

So maybe you should go up to a 21 pitch?

MarkB

NRath - how do you know you were going 3600 rpm?  Don't rely on the gauge.

Michael T

If you think your tach may be off you could probably borrow a shop tach from your service dealer. Remove your gauge and swap them. When I used to do a lot of my own engine tuning I had a spare rpm gauge that I knew was reliable with about 8 feet of wire that had alligator clips on the end. It made for an easy tach check.

mvn

Agree with Michael.   Get your hands on a reliable tach.  Just today I was wondering why my rpm was so high yet I wasn't going anywhere...... Until I did the Faria "tap".

Mark

mvn

In this thread,  you will find an Excel spreadsheet that calculates optimal prop pitch based on a few variables. 

http://rinkerboats.vanillaforums.com/discussion/comment/4845#Comment_4845

Mark

NRath

10-4, I can dig deeper into that.  The tach in it is brand new Faria.  PO replaced it just before I bought it.  Only had 1 hr on the clock.  The original had just quit working.
Also, the outdrive ratio is 1.79.

Pulling a tube or single skier tonight, it really seemed to struggle getting up.  So much that the admiraless noticed and blessed smart tabs without me bringing it up.  Had 2 in bow, pass seat, and myself- nobody in rear.  And, a full tank of gas

MarkB

New tachs need to be set up properly. 

mvn

MarkB said:

New tachs need to be set up properly. 

Good point.   Yes,  you need to have the right cylinder count set correctly. 

Mark 

Michael T

Many analog tachs used to be adjustable through a small port on the back of their housing using a jeweler's screw driver. It was amazing that some of them could be out of adjustment by 100-200rpm just by where the needle was in reference to the metal pin at the 0 rpm designation. Anytime a friend installed a new tach we used a reference tach to calibrate it. The only tach that I have never heard a calibration complaint with is the Gaffrig tachs. They seem to be flawless.

pepmyster

Just to note, this week-end, I payed attention to rpm and speed. 08 280ec 8.1 Merc, 24 pitch props, 3800 rpm at 35 mph. If that helps anyone.

Michael T

That sounds good pepmyster. What are your rpm and mph at wot with that 496?

NRath

We could drop that big boy (8.1) in the 19'er!  I bet it would stand on end like a bobber!  lol.

I spotted the cyl adjustments on the back of the old tach last night when looking for adjustment options, but didn't have time to pull out the one in the boat to check it.  Spent too much of the evening having dinner on the lake  

Another thing I looked at yesterday- the spray.  At about 40, I saw the spray was exiting the side of the boat about 12-18" behind capt chair.  Slowing down into the 20's brought it up to even with capt chair.  I'm guessing that's only really relevant for discussing trim, right?  Or, are there some other takeaways from the spray pattern?

Michael T

Yes, NRath you are correct. The spray pattern is relevant for trim, total load and side to side load. Spray patterns from the transom or wakes can also tell a lot about the boats attitude and set-up. I remember years ago a buddies boat with an uneven wake that just looked weird. We adjusted loads etc to balance the boat but the wake still looked weird. Closer measurement showed the transom plate of the engine was not square to the hull. As someone mentioned in a post a couple of days ago wake differences (patterns) with twin engine boats can be a telltale sign of problems. You are wise to note the attitude of your boat, that way you are more likely to notice a change.

pepmyster

Haven't tried the wot  in awhile, but when I do......................YAHOOOOOOOO!!!!! Next time I'll check my data.......... 

Michael T

All right pepmyster - I LIKE that! :-)

NRath

I can confirm the Faria tach has an adjustment screw in addition to the cylinder setting.  Unfortunately I'm still trying to hook up with a 2nd tach I trust for calibration.

NRath

Change is in the wind.  Following you guys suggestions, the smarttabs are on the way.  Also jumping in with a 14.5x17x4 prop  (currently a 14.5x19x3).  The loss in top speed isn't an issue.  The only time it gets close to high revs is when the prop cavitates in turns when trying to sling the kids off the tube.  The 4 pedal is supposed to help that a little also.  
The only bummer is that both will be here about the same time and I'd really rather try one at a time to get a feel of the difference of each.  Only got about a week left with the daughter before school starts, so I'll be all in as soon as i can.  I can swap back to the 19x3 in the fall.

Michael T

When you say smart tabs do you mean they adjust themselves (spring loaded) or helm adjustable? Any tab should make a difference but I like the captain adjustable from the helm better. It will be interesting to see what the new prop does. I had a 4.3 LX (as I said before) we used to call a 17" pitch prop on that boat a ski prop as it gave a better hole shot to pull a slalom skier out but less top end. We also had to be careful that we didn't over rev the engine as that prop would increase the rpms by 200 rpm at wot. I would think the 4 blade will drop the revs so you might not over rev but you may want to make sure that you don't lug your engine with too much prop for the engine. It takes more grunt to turn a 4 blade.

NRath

Due to budgetary constraints, I had to go with Nauticus "SmartTabs"- the automatic style.  I would def have preferred helm adjustable trim tabs, but I was seeing about 6-700 for those.  Got too many other boat expenses getting it all setup to get everything I want now. I figure if I do decide to upgrade in the next year or two, I can probably sell these for a few $$ back out of them.  $130 with 5yr warranty wasn't too hateful either way.
Sounds like we're on the same page prop wise.  I read that going to a 4 blade, dropping 1" of pitch would be about equal to a 3 blade.  I need more out of the hole to boot, so going down 2" seems like a good thing.  Hopefully I'll get the good ski prop out of this.  I just wish I had ordered it a week earlier!
I'm staying well clear of 4400 rpm's for now until I get a second tach to verify my Faria reading.  3400 on the Faria is about the limit at this point, which gets me to 45 mph (lake speed limit).  The engine sounds fine at this, or whatever rpm it's running.  I'm a lifelong gearhead, so paying attention to how it sounds and feels is second nature.

Related question- do V-P and Mercury have rev limiters on their engines?

Michael T

212 and Al can jump in here, but I thought the rev limiter was set for your engine at about 5K. That said, imo, rev limiters are a bit of an aw sh*t gauge as you can do a lot of damage before they stall-out your engine, for example if the captain is wave hopping and the prop is spinning wildly out of the water. imo rev limiters are meant for normal use problems. BTW I worry as much about over-propping an engine with too "tall" a prop and lugging it, particularly under loads (skiing & tubing) because the prop will not let the engine fall into its proper rpm range at wot. I always want to know what rpm band my prop will let my engine operate in at wot. that tells me a lot about how I can and should drive the boat.

69fastback

The Nauticus Smart tabs are great, and they will help your boat plane faster, and reduce bow rise. They're a large improvement over having nothing. 

NRath

Got them installed and made a 1st run.  It wasn't an apples to apples run as I had an extra person (~200#'s) and the 14.5x17x4 installed.  That said, all combined there was a HUGE improvement!  My next trip will be minus the passenger and I may switch back to the 14.5x19x3 for a test.
With 2 in the bow, 3 in the cockpit, there was very little bowrise.  Probably reduced by 75%-   Granted the extra 200#'s in the front was part of that.  In later starts, I did experience some bow rise with 2 on tube and maybe one in bow, but easily 1/2 what was typical before.  The admiral was able to notice the difference and commented on how much better it was both in bow rise and ease to plane.  My point there is that if a non-driver notices, it has to be pretty significant.
RPM's were obviously running higher given the pitch change.  I never got it would up over about 3500.

I will get some good #'s in the near future for comparison.

mvn

Great news........but hardly a surprise!  The lack of significant bow rise is very noticeable as well as the reduced time to plane and minimum planing speed.  I'm amazed though that you're able to run a 17" prop without ridiculous RPM readings.  I tried an 18" 4-blade cupped stainless on my previous 192 that had a 4.3L Volvo SX-M. It pulled like a tractor but the WOT was way too high.  You really couldn't do much higher speed cruising.  I ended up settling on a 20" 4-blade cupped stainless for all 'round performance and it has stayed that way ever since.  The boat came with a 4-blade aluminum but I forget what the pitch was....maybe 19"?

Yes, weight distribution will make a huge difference as well in the 192.

Mark