Advice on re-powering 30' Portsmouth

gmac

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Hello all, fairly new here but have followed this forum allot the last few months. I have recently purchased a 30' Portsmouth (Sisu). Its in great shape for its age but will be doing a fair amount of work to it. Removing flying bridge, painting exterior, sprucing up the interior among a few things.

Which leads to my main question. It is currently powered by a Cat 3208 320 hp with 1000 hrs on it. It runs great, the hr or so I have spent on the boat. 1 1/2" dia. shaft, 20 wheel. Not sure on pitch or what gear it has. Boat tops out at about 16 knots, cruises nice about 12.

Been thinking that while we are into it, I might re-power with a lighter, more hp engine. If going to do it would like to get to a 18-20 knot cruise. Not sure if that is possible with this hull or not.

Been thinking a QSB5.9 480 hp. Which brings up allot of questions, will a 20" dia. prop be OK? thinking could lower the shaft and jog the metal skeg ? ( not sure if that's correct term) down and install a new larger rudder to aid a larger wheel. 1 1/2" shaft sufficient? Its recreational use, maybe 100-150 hrs a year.

Would be interested in what your suggestions would be.

Maybe to get the picture on why I would re-power with a good running engine. I live in Utah now ( born and raised in Eastern Canada) and where the work be done on boat. When finished will make its way to Alaska where it will call home, either Seward, Homer or Whittier. I can do all the work here where as when it gets to Alaska will have to hire out. Seeing the cost to have this done got me thinking, expressly in Alaska..

Sorry about the long post, look forward to you opinions.

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Dr Dude

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blinsquirrel

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Great looking boat! I have a 30' sisu with a 250 hp Volvo swinging a 20x21 dyna-quad. Not too much room to swing a larger wheel...but the newer DQX may offer better performance with the limited tip clearance. They built these hulls with those fat fiberglass rudders. I bet if you went with a streamline rudder alone you could gain a knot...those things are fat! That's a great engine you have in the boat...barely broken-in. I would wait and see how she performs without the bridge. My boat was built light compared to a cruiser...not sure what extras you have in the boat. I cruise 16.5kts at 2400 and top out around 20.5kts at 2800.
 

steveinak

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Hi buddy:D got yourself a nice looking boat !! Leave it alone till you run it here for awhile. Seems to me if you can do a repower home you could do one here, trailer the boat here to my place, plenty of room, and do the repower, just ship up a motor or haul it up in your truck. See ya when ya get here.
 

gmac

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Ya, you guys are probably right, leave well enough alone and just enjoy it!! Allot of $$ and work for a few knots. As you can see in picture motor looks in great shape, no corrosion at all.
The boat is not light but has allot of comforts for size. 4.5 KW gen, 75 gals fresh water, heat/AC, stand up head with shower, electric stove, fridge etc. This is what drew me to this boat, easy to spent several days aboard with out going back to port.
That's a good point on rudder, I was surprised it was fiberglass. How thick of stainless are they typically on this size of rudder? 3/16 or 1/4"?

Thanks for replies.

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gmac

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Hey Steve, thanks! and hope to meet you up there. You probably remember me, I called you on your H&H. I was going to build the kit boat but when seen this and the cost difference from a new build, I couldn't justify it as much as I wanted to for the few weeks or month a year I plan on using it.
I'll be by to see you for some shrimp pots, nothing better then fresh shrimp at sea!!
 

steveinak

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Hey Steve, thanks! and hope to meet you up there. You probably remember me, I called you on your H&H. I was going to build the kit boat but when seen this and the cost difference from a new build, I couldn't justify it as much as I wanted to for the few weeks or month a year I plan on using it.
I'll be by to see you for some shrimp pots, nothing better then fresh shrimp at sea!!

That is a beauty, you'll be able to stay out a month at a time easy !!! Green & white so we can raft up together in shittier(whittier) You are going to trailer it ?? If you need a place to winter store it let me know, its nice and dry here all winter, no mold or freezing rain to deal with like the waterfront towns, tarp it good and open all the hatches so she can dry out good.
They are just waiting to be caught
gloved shrimp cropped.jpg

gloved shrimp cropped.jpg
 

gmac

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Having shipped here then will build a trailer for it. I do have friends in Anchor Point and Ninilchik that I can store it to, but will keep it in mind.
 

MDI45

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Nice lookin rig....I would not touch that motor....1000 hrs for that 320hp 3208 is nothing....That is one of Cats best moters...take care of it and it will last a long time ...Good Luck
 

captainlarry84

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Nice Rig!

Nice looking boat. As for your 3208 T @ 320 HP I am surprised that she is so slow. I would do some research and see about picking up a knot or two.
Being that we know the diameter is 20 using my math the pitch of your wheel should be 18. If you are swing less pitch than that something is wrong. Also your reduction gear is a 1:53. In addition if you are swing a 20 X 18 and top out at 16 knots at 2800 RPMs your propeller efficiency is only 60%. It should be about 75% which would put your top speed at: 19.5 to 20 knots.
I would do the following:
#1 Start with all fresh fuel filters.
#2 Free gear the motor to WOT it should rev up to almost 3000 RPMs.
#3 Make sure that with the throttle fully advanced that you are hitting the throttle stop on the injector pump..
#4 Photo tach the boat to make sure you are getting your 2800 RPMs & the boat tach in correct.
#5 FYI: Pitch on your wheel with a 1:53 gear and a 2800 RPM rated motor each 1 of pitch will reduce you by 200 RPMs
#6 Consider replacing that fat glass rudder with a S/S or bronze one. The thinner rudder will allow water to escape when you no longer need it which should improve efficiency.
#7 Your boat has a wet tube assembly. Therefore I would consider adding about
3-4 to your wet tube and extending the shaft. This would get the wheel away from the keel for better water flow and performance. I did this on two DE boats and it worked nicely. Getting the wheel a little away from the keel will allow the propeller to catch more water and increase efficiency.
#8 If the motor runs as good as it looks I would exhaust all of the above before pulling out on of the finest power plant that CAT ever made. Out of all 3208s the 320 was the best.

In closing I would value your 3208 w/gear at 8~10 k. You have a fine looking vessel.

PS: I see a white Fleet guard fuel filter.USE ONLY CAT FILTERS for fuel & oil. They are by far the best to can buy.
 

gmac

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Thanks for all your input. I will be spending a week in FL on the boat so will try what you have mentioned and let you know how it works out.

Thanks again.
 

BillD

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Hey Steve, thanks! and hope to meet you up there. You probably remember me, I called you on your H&H. I was going to build the kit boat but when seen this and the cost difference from a new build, I couldn't justify it as much as I wanted to for the few weeks or month a year I plan on using it.
I'll be by to see you for some shrimp pots, nothing better then fresh shrimp at sea!!

Gary,

It was good talking with ya on the phone last week.
IMO I'd run that CAT until it don't run no more. Most likely
it will run for the life of the boat.

If you do go nuts and change it out....and if you can handle about the same diesel smoke the CAT puts out......bolt in a Cummins RECON 6BTA 370 with a ZF 220A gear.

Simple motor, reliable and "relatively" cheap !

Keep the CAT....btw, will you have a "height" issue hauling the boat over the roads out to Utah ??

Bill D
 

captainlarry84

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Thanks for all your input. I will be spending a week in FL on the boat so will try what you have mentioned and let you know how it works out.

Thanks again.

One thing quickly. Is you boat turning up the full 2800 RPMs? are you basing your 12 knot cruise speed at 2400 RPMs. CAT 3208s must get 2800 RPMs or they will fail down the road. In fact all diesel must get all of the rated RPMs. Without obtaining the rated RPMs the motor carries great load and every RPM. Great load is heat. Heat is the kiss of death.
3208 CATs are drilled a tapped for pyrometers a great addition to add. For the 3208 I like the isproo dual probe gauge.
The pyrometer tell it all.
 

gmac

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I have a photo tach and will check it out, I have just gone off gauge which was 2800 WOT and cruise was about 2400. Temps did seem a little low, about 165 but will verify that as well.

Bill, I am going to remove the flying bridge, permanently actually and going to add a second station to deck area.
 

MASTERENEGADE

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Leave the cat in the boat and run her. I have the same motor and by no means am i a mechanic and this is engine is simple, efficient, and runs the same every time. I have almost 2900hrs and has never given me any issues. The motor i have will prob rust and fall apart before i ever reach 10,000hrs. :)

165degress isnt too cold for this motor, i am a hair over wheeled rite now with a 4blade 23x23 and when cruising 500 off top end my temps hold steady around 170, if i back off a lil and run say 600-700 off top she stays around 165 and that is being over wheeled by about 150-180rpms depending on the carrying load.

Larry has alot of great points and has helped me out as well.

Good luck with the beautiful boat if you sell the engine let me know i'd buy it in a heart beat and give it a good home
 
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