underpowered and frustrated

OldSkool said:
You'll love this. I have been following the rebuild of PT 658. It is a wonderful boat that is completely restored.

http://www.savetheptboatinc.com/index.htm

No Arab names on this boat thank you.
Click to expand...

Bill, thanks for sharing this with us. I found it a facinating read but two things really surprised me about WWII PT boats. First I didn't realize they had wooden hulls. I always thought of them having armor plate on the sides. Second, that the engines were gasoline instead of diesel.
 
Pull that 6.2 and put this in!!!

Propulsion
3 5M-2500 Packard-Marine V12 Engines.
These engines are 4 stroke, water cooled, 60 degree, V- type with a 6-3/8" bore and 6-1/2" stroke, for a total of 2490 cubic inches of displacement. Each engine has 48 valves, 2 inlet/2 outlet per cylinder. They have a compression ratio of 6.4:1, and are fitted with a gear-driven centrifugal supercharger and intercooler. The engines are installed with a Holley 1685F aircraft-type carburetor, and use aircraft- type dual magneto sparks, with 2 spark plugs per cylinder. The engines develop 1500 Hp at 2500 rpm.Max revolutions is 3000 rpm. Engine weight is 3100 pounds. These engines were designed to burn 100 octane aviation gasoline to achieve nominal power output.
 
Daddubo said:
Pull that 6.2 and put this in!!!..
Click to expand...

That engine would make my 320 a hydroplane. Another feature of those engines that caught my attention was the 4 valve design. I don't think 4 valve auto engines were that common until the '80's and these were around 40 years earlier.
 
320Bob said:
That engine would make my 320 a hydroplane. Another feature of those engines that caught my attention was the 4 valve design. I don't think 4 valve auto engines were that common until the '80's and these were around 40 years earlier.
Click to expand...
Those motors are about as big and heavy as your 320 - an old timer I know found and restored one of these motors - they have it mounted on an old railroad cart for show - quite impressive
 
320Bob said:
That engine would make my 320 a hydroplane. Another feature of those engines that caught my attention was the 4 valve design. I don't think 4 valve auto engines were that common until the '80's and these were around 40 years earlier.
Click to expand...

Well back in the day Packard, Kaiser, and Hudson, Nash were all ahead of their time with engines and cars. I loved the 52 -54 Kaiser's my Dad had a 52 they were big and cool looking.
If you never saw one here is a web site about some.
http://oldcarandtruckpictures.com/Kaiser/
 
techmitch said:
Well I guess it's time for my suggestion.
http://www.fas.org/programs/ssp/man/uswpns/navy/specialops/markv.html
And just think, only about $7800.00 to fill her up!!!
Click to expand...

I was on the Delaware River in Philadelphia about 2 years ago when they were out testing that boat... on all days but July 4th weekend.

They caused such a big wake several times going by marinas. Several people were on their radios telling them to slow down and be aware of what they were doing... the radios remained silent on their end. Aholes!

Sick boat nonetheless though!

Doug
 
320Bob said:
Bill, thanks for sharing this with us. I found it a facinating read but two things really surprised me about WWII PT boats. First I didn't realize they had wooden hulls. I always thought of them having armor plate on the sides. Second, that the engines were gasoline instead of diesel.
Click to expand...

The wooden hull was to prevent contact with magnetic mines and they could be used as mine sweepers. The wooden hull was quite bullet resistant.

The Packard engines of that day created power faster than diesels of that vintage. The ability to get on plane quickly was a matter of staying out of harms way.

Of course this is all from what I have read and have been told by my dad and uncle who were old salts back in the day.
 
plenty of room in the tunnels for 18 x 18........want to go 4 blade for some more docking control.......factory prop is a 17x 19 3 blade.......what do you think the effect will be.....WOT is currently 5200 with the last 500 doing absolutely nothing for additional speed.
 
Mutual Fun said:
plenty of room in the tunnels for 18 x 18........want to go 4 blade for some more docking control.......factory prop is a 17x 19 3 blade.......what do you think the effect will be.....
Click to expand...

A good prop shop should suggest which 4-blades props will be good for your boat. Yes, 4 blades props will improve handling and the hole shut. So, if that's your goal it will most likelly be acheaved, at last these were reports from other members that switched from 3 to 4 blades on 320s.

Mutual Fun said:
.....WOT is currently 5200 with the last 500 doing absolutely nothing for additional speed.
Click to expand...

If your engines are 4800 rated I agree that you're underproped at 5200RPMs. To gain more speed and lower RPMs to meet the specs all you need is to tune your props. A good prop shop will do this magic with ease and you'll be surpised with results.
 
Mutual Fun said:
plenty of room in the tunnels for 18 x 18........want to go 4 blade for some more docking control.......factory prop is a 17x 19 3 blade.......what do you think the effect will be.....WOT is currently 5200 with the last 500 doing absolutely nothing for additional speed.
Click to expand...

I second Alex's recommendation to go to a prop shop to determine what would be the best size 4 blade prop for your boat. Also do you get the same rpm at WOT on both sides or is there 100 rpm or so difference like there is on my boat. If so, the pitch on the slower prop may have to be reduced.
 
You must log in or register to reply here.

Forum statistics

Threads
113,170
Messages
1,427,746
Members
61,079
Latest member
capeharj
Back
Top