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TOPIC: 4788 vs 4588

4788 vs 4588 12 Jul 2017 04:08 #26

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Our boat had the bow pulpit removed by former owner. They did a nice job and I like it. From the back of the swim platform to the end of the shortened bow pulpit is 50'.

We looked at both 45 and 47's. I like them both for much of the same reasons listed above. However, out of all the 45's we looked at, many were not well maintained. There were not many in good shape. There seemed to be more 47's in better shape so there was a bigger pool to select from.

I think either can be a great platform if they have been taken care of. Good luck!

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2000 4788 w Cummins 370's, underhulls, swim step hull extension
12' Rendova center console with 40HP Yamaha
MV Kia Orana
Currently Alameda CA

4788 vs 4588 12 Jul 2017 04:42 #27

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The 47 has a vastly better ride/attitude compared to the 45, regardless of power plant.
If you cruise a lot, get the 47. If you don't, get the best boat.

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Tally and Vicki
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4788 vs 4588 12 Jul 2017 04:55 #28

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my 1994 - 4788 serial number indicates it was built in July of 1993 as a 1994 model. the serial range is BLBA18 which { I think} means it is the 18th one built ? Anyway, my boat definitely has foam cored decks which are mostly solid. I do have an area of delam about 2 sq ft aft of the Starboard hatch on the foredeck. I believe this is a production delam , and I am not worried about this at all. I recently sold a 1997 -4788 with the same issue near the port side aft of the Pulpit, again the surveyor was not concerned.

Just FYI...
Cheers, Gary

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Afterglow
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4788 vs 4588 12 Jul 2017 13:30 #29

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There is no doubt that the Cummins 6B can achieve a very long life in service if the engines parameters are followed and the maintenance schedule is kept up.
These are some of the items that need to take place for that to happen in roughly priority order, in other words this is what I would do if it were my boat:

For the 370 Cummins as example only
Basic loading
- First ensure accurate tachs, gages and a full complement of stores as your boat would typically be used
- Make sure the engines can achieve rated rpm plus 3-5% as a brief test fully loaded on a hot and humid day (3,090-3,150 rpm)
- Add pyro and boost gages ASAP
- Use the engine specs guide to make sure you never exceed the EGT temps by more than 20 degrees above rated temps
- You can then run the boat safely at 300 rpm or less off of the top

Engine items other than scheduled
- Replace the raw water pumps with sea max pumps
- Remove service and replace the intercoolers with correct grease and test for leaks
- Inspect and potentially replace the trans coolers (if more than 8 seasons replace)
- Figure you best strategy for blowby collection , I favor sbmar’s approach
- Remove the fuel coolers and add block off plates

How I would run the boat and look at life
- Load and prop the boat so it can always reach 3,100 minimum
- You can then run the boat at up to 2,700 safely
- I feel better about running at 2700 on a boat propped for 3100 then a boat propped for 3000 running at 2600
- If your boat is propped to reach 2900 it is not typically safe to run at 2600 or 2500 or even 2400
- Max high speed cruise should be demanding no more than 180-200 hp per engine or 10-11 gph per engine
- Always watch the EGT gages for the max reading especially in hot and humid weather when you will see readings rise

With just a little attention these engines should live much longer than most owners are ever likely to own the boat.

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Northport NY

4788 vs 4588 12 Jul 2017 13:37 #30

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weiss wrote: my 1994 - 4788 serial number indicates it was built in July of 1993 as a 1994 model. the serial range is BLBA18 which { I think} means it is the 18th one built ? Anyway, my boat definitely has foam cored decks which are mostly solid. I do have an area of delam about 2 sq ft aft of the Starboard hatch on the foredeck. I believe this is a production delam , and I am not worried about this at all. I recently sold a 1997 -4788 with the same issue near the port side aft of the Pulpit, again the surveyor was not concerned.

Just FYI...
Cheers, Gary



Hello Gary - I have seen a 47 out here just recently headed out to view the July 4th fireworks locally with 26 pob.
Many crowded the foredeck and were watching the show not realizing that they had maybe close to 2,000 pounds up there.
I was asked to look at the boat at the marina last week and it had a fairly large delam near a hatch - not surprisingly.
In past posts and in real life I have seen this problem when folks really overload small areas of the boat.
Sometimes due to a heavy dinghy and small/poor davit bases, crowds and 'unusual' furniture on the flybridge and show crowds like this one.
I have yet to see a situation where this problem spreads or gets worse due to the damage but I guess it is possible especially here were we get freezing temps.
Never have I seen this so far where it was not avoidable with a reasonable approach of use.

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Northport NY

4788 vs 4588 12 Jul 2017 13:43 #31

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DryMartini wrote: The discussion on engines is helpful in making a decision. I boat on the upper Mississippi, and finding an experience diesel mechanic is difficult. Mechanics with experience with Hino truck engines are reluctant to work on marine engines. The discussion on overloading is something I never thought about. My understanding was that diesel engines should be run about 10% of the time at WOT. Maybe this is not true.

Another factor that was raised that I had not really considered is the true overall length of the boat. I have a 50' slip, and I am allowed to extend 3' beyond the fingers. What is the actual overall length of the 4788?



Please see post #29 above as it applies to all diesel engines for the most part.
Consider calling Earl if you get a good candidate with Hino's.
FWIW - I have owned these diesels over the years (some terrestrial some marine)...LeManns, Perkins, GMC, Navistar, Hino, Cummins, CAT, Lister Petter, and a Yanmar. I find the Hino the easiest to work on and the most robust of them all. I have also worked on a bunch of other diesels for friends over the past 30 years or so.
YMMV

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Northport NY

4788 vs 4588 12 Jul 2017 17:10 #32

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smitty477 wrote: There is no doubt that the Cummins 6B can achieve a very long life in service if the engines parameters are followed and the maintenance schedule is kept up.
These are some of the items that need to take place for that to happen in roughly priority order, in other words this is what I would do if it were my boat:

For the 370 Cummins as example only
Basic loading
- First ensure accurate tachs, gages and a full complement of stores as your boat would typically be used
- Make sure the engines can achieve rated rpm plus 3-5% as a brief test fully loaded on a hot and humid day (3,090-3,150 rpm)
- Add pyro and boost gages ASAP
- Use the engine specs guide to make sure you never exceed the EGT temps by more than 20 degrees above rated temps
- You can then run the boat safely at 300 rpm or less off of the top


Ron - do you know the rated exhaust temperature for the 370hp 6BTA? Just wondering what I should use as a "hard stop" termperature now that I have EGT sensors.

I have seen EGT creep up since I tested WOT with fresh bottom paint back in April. Back then I did not exceed 1000F at WOT. This past weekend I saw 920/960F (P/S) at 2500rpm, 16 knots, full fuel and water. Wish I could remember the boost pressure but I was busy navigating through a bunch of slow moving sailboats. Props are 24x23.

Thanks.

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Evan
2001 Bayliner 4788 "Fifty / Fifty II"
League City, TX

4788 vs 4588 12 Jul 2017 17:21 #33

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egbauman wrote:
Ron - do you know the rated exhaust temperature for the 370hp 6BTA? Just wondering what I should use as a "hard stop" termperature now that I have EGT sensors.

I have seen EGT creep up since I tested WOT with fresh bottom paint back in April. Back then I did not exceed 1000F at WOT. This past weekend I saw 920/960F (P/S) at 2500rpm, 16 knots, full fuel and water. Wish I could remember the boost pressure but I was busy navigating through a bunch of slow moving sailboats. Props are 24x23.

Thanks.


I run a bit less than 900 at the same 2500 RPM. Engines are 330's but that should not matter.

Even at WOT of 2900 (approx) with full fule and water I do not exceed 900

What RPM can you get to with full fuel, water, etc...???

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KEVIN SANDERS
4788 LISAS WAY
SEWARD, ALASKA
www.mvlisasway.com
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4788 vs 4588 12 Jul 2017 18:14 #34

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Kevin - I exceeded 3000 rpm on both engines right after the bottom job. Did not test it this last time out. I don't think I would have hit the 3000 mark.

I think your props are pitched at 22" or maybe even less? Guessing that is the big difference between your boat and mine.

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Evan
2001 Bayliner 4788 "Fifty / Fifty II"
League City, TX

4788 vs 4588 12 Jul 2017 20:07 #35

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Hello Ed- I am traveling and do not have access to files and have a crappy memory lately. I just looked this up as well about 2 weeks ago for someone on the BOC but cannot remember the number.
You can look it up yourself by going on Tony Athens site sbmar.com and clicking on the tab for engines then on your engine and then click on the download for your detailed performance specs . Each engine is different as is Cummins, Hino , Volvo, Yanmar etc and after a while I cannot remember them individually.
This data for Cummins is typically spec'd out as a reading immediately AFTER the turbo outlet and not before the turbo itself and it will say that on the Cummins performance spec sheet. There are a FEW that do spec it out as a reading before the turbo so please read that carefully as well.
So far - I have never seen a Cummins 370 that cane reach 3100 that has a pyro problem, of course once I post that a member here may have an exception for us but for the most part that is the cheapest and easiest test for load.

Kevin - your numbers look great and you can still travel fast as you like. Enjoy that setup forever or until you get tired of it and move on.
Please remember Kevin's 2900 is the same as if the 370's are reaching 3100.
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Northport NY

4788 vs 4588 12 Jul 2017 20:14 #36

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" I think your props are pitched at 22" or maybe even less? Guessing that is the big difference between your boat and mine."'

FWIW - my Hino's were pitched at 20.5" and scanned just a tab more aggressive than that.
We started with higher pitch props and moved down and balanced these I the 1st season.
24 x 20.5 x 4 blade Nibral
The Hino is rated at the same 3,000 and had the same 800 series Hurth at 2:1 ratio.
I could always reach 3,100 and used to tow a larger RIB with no issues.
At max WOT for brief tests the speed would be about 22 knots at 3,100+.

Speeds from 2400 to 2800 were about (OK not really but close and easy to remember) the same as walking up from 14 knots each 100 rpm,
2400/14 , 2500/15 , 2600/16, ,2700/17, 2800/18
If you wanted to get real detailed the speed was a bit slower than 14 at 2400 and a bit faster than 18 at 2800 but its easy to remember this way.
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Northport NY

4788 vs 4588 12 Jul 2017 21:25 #37

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Ron - indeed I found it on Tony's website. The number is 890F or 900F depending on when the test was run (2000 or 2003). Either way, I would say that the 960F that I measured on the starboard side is too high. My EGT measurement is done via the port that is in the riser manufactured by National Marine Exhaust.

Guess I should put new props on the to-do list. Given that I'm at 23" pitch now, what would you recommend for a new prop pitch? 21"?

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Evan
2001 Bayliner 4788 "Fifty / Fifty II"
League City, TX

4788 vs 4588 12 Jul 2017 22:27 #38

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egbauman wrote: Kevin - I exceeded 3000 rpm on both engines right after the bottom job. Did not test it this last time out. I don't think I would have hit the 3000 mark.

I think your props are pitched at 22" or maybe even less? Guessing that is the big difference between your boat and mine.



Bought new 21" props last year. About $3700 at a place called "the prop shop" same Nakashima props the factory used.

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KEVIN SANDERS
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4788 vs 4588 12 Jul 2017 22:59 #39

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"Guess I should put new props on the to-do list. Given that I'm at 23" pitch now, what would you recommend for a new prop pitch? 21"?"

The best answer I can give you is not likely the one you want to hear.
The largest problem with your question is that props are not all the same (blade area, rake, cup, edge bevel, etc) .
When we talk about props that are 24 x 21 we do not mention that there is a large difference between two props both labeled 24 x 21.
Even if they are from the same manufacture the exact model matters so we cannot compare apples to apples with these numbers.

The next two smaller problems are that no two engine sets are the same and no two boats demand the same hp for cruising. So even if I took off a set of props I know works for boat "A" it may be to aggressive for boat "B" give the differences in engines, weights, hull etc.

The good news - once you have a good baseline on your set up you can prop your boat with the help of a good prop shop.
- Your boat engines are tuned up
- Your boat is at heaviest weight
- Your boat is run on a hot and humid day
- You take accurate tach readings at WOT with the above variables

Then you take your existing props with your trans ratio and all the data from your run to a prop shop and they will help you 'get' the rpm that you ask for.
I always tell them to make sure they get me the full rom that I am aiming for - not just get me near that. So they know that I am not worrying about having slightly too 'little;' pitch for some unknown reason.

Note - the general limit for changes to 24" diameter props is for a maximum 2" pitch change. That is if your props start at a pitch of 24" then the max change would be 22". Since they can only change the outer edges of the props and not the prop root then the affects of bending the outer blades become less affective the further you travel from the original design.
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Northport NY

4788 vs 4588 13 Jul 2017 00:56 #40

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Ron - if I order new props, I figured I'd just go to the same shop where Kevin bought his. But I did call the local prop shop and ask them whether they could re-pitch down to 22 or 21" and they assured me that it was no problem. I was not aware that they could actually calculate the correct pitch given my current WOT rom and the 3100 rpm target so will certainly talk this over with them.

I think I've met all of your criteria. The engines have been tuned, the boat has full tanks and it's always hot & humid on the Texas gulf coast. My tach readings are electronic based on the pulses from the flywheel (like the Aetna tachs).

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Evan
2001 Bayliner 4788 "Fifty / Fifty II"
League City, TX

4788 vs 4588 13 Jul 2017 21:16 #41

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The brochure I am holding was printed July 1997 and lists the 47 as centerline 47'4" and overall (including bow and transom platform) at 54' 0".
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4788 vs 4588 14 Jul 2017 00:21 #42

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"But I did call the local prop shop and ask them whether they could re-pitch down to 22 or 21" and they assured me that it was no problem. I was not aware that they could actually calculate the correct pitch given my current WOT rom and the 3100 rpm target so will certainly talk this over with them."

A good prop scan shop will scan you props and take your goal and do their math.
I am always surprised when I get props scanned as they are never the exact same as what they are stamped even when new.
A 24" D prop may actually be 23.7 or maybe 24.2 but hardly ever 24 / same with a 23" pitch.

So by taking your exact props they can better determine what you have so they are much better equipped to know what you need to go to.
That is true whether you are repitching existing props or purchasing new props.
So even of buying new it often makes best sense to scan what you have now that is giving you your baseline numbers

And ....fwiw ... I learned this all the hard way.

When you are not overloaded ALL of these things typically happen:
- engines are safe and happy
- fuel use per mile goes down
- engine heat is reduced per hp extracted
- more total hp is available per engine
- Often your WOT top speed increases (but at a higher rpm)
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Northport NY

4788 vs 4588 30 Jul 2017 22:25 #43

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Ron - these are the numbers I got after having a diver clean the bottom and the running gear. Props are 24x23".

RPM at WOT: 2900
Boost at WOT: 27 psi
EGT at WOT: 975/1020F (P/S)

I'll bring this to the prop shop and tell them to re pitch so I get 3100 at WOT.

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Evan
2001 Bayliner 4788 "Fifty / Fifty II"
League City, TX
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