T Jason 28 repower ??

sandytows

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I have a 2001 TJ28 with a cummins 210 and with 6000 hours it is getting close to repower time.
Currently the boat performance is as follows.
ZF220a 2.0:1 Gear with 22"x24" prop with moderate cup.

2200rpm 16-17kts cruise
2600rpm 20-21kts WOT

The boat is used commercially as a water taxi and frequently carries 6-7 people plus gear, but not always.

I would like to get the cruise speed up to 20kts with average load of4-5 people. Top end I don't care about, but the boat must have enough power that a 20kt cruise is easy enough on the engine that it will last me 5000+ hours.

Can anybody offer up suggestions of engine and gear package to get my desired performance?
 

BillD

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25 Terry Jason with Cummins 370 power
Informative Post

I have a 2001 TJ28 with a cummins 210 and with 6000 hours it is getting close to repower time.
Currently the boat performance is as follows.
ZF220a 2.0:1 Gear with 22"x24" prop with moderate cup.

2200rpm 16-17kts cruise
2600rpm 20-21kts WOT

The boat is used commercially as a water taxi and frequently carries 6-7 people plus gear, but not always.

I would like to get the cruise speed up to 20kts with average load of4-5 people. Top end I don't care about, but the boat must have enough power that a 20kt cruise is easy enough on the engine that it will last me 5000+ hours.

Can anybody offer up suggestions of engine and gear package to get my desired performance?

How about a "plug and play" 6BTA 370.
Use the same gear (if rated for 370 hp) or a different gear with same ratio.

Use can cruise a 370 @ 2500 rpm and get your speed.

Nice pricing on 6BTA 370 RECONs, same footpring as the 210

What does the boat have for a prop diameter ?

btw, this post is very helpful to me.

I just bought a 25 T Jason and would like to obtain a 16-18 knot cruise with a 6BT 210 with a 2:1 gear and 22 inch prop.

With your 28 T Jason running numbers it sound achievable.

Question? What do you figure your boat weighs full fuel, gear and 6-7 passengers?
 

captainlarry84

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You will need about 300 HP to get 20 Knots. If your current shafting is 1.5".
I would go with a 315 Yanmar. Your wheel would be about the same maybe a 22 x 23 except you would spin it a lot faster.
 

sandytows

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I have 1.5" shafting that I will upgrade to 1.75.
I have had my eye on a Cummins 6BTA315 recon.
I don't know much about the 315 yanmar what model is it? and what displacement?

Bill, got your PM will call you today or tomorrow
 

jojobee

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The 6LPA-STP 315 is no longer available, however we have the next generation 8LV320 with commercial status. We have successfully been putting these in fire boats, parasailboats, and other commercial applications.
 

BillD

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25 Terry Jason with Cummins 370 power
The 6LPA-STP 315 is no longer available, however we have the next generation 8LV320 with commercial status. We have successfully been putting these in fire boats, parasailboats, and other commercial applications.

sandytows,

I suggested the Cummins 330 or 370 (370 is a better buy for the hp) because the Cummins RECON 6BTAs are the ONLY mechanical marine diesels still produced (99.999% new).

If you move to an electronic EPA Tier II or Tier III engine your are increasing cost and complexity.

FWIW, Bill D
 

captainlarry84

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KristenFormer Charter Captain
Shame the LPA 315 was a winner. Plus it was a mechanical motor which kept the price down. I would research & see if Mac Boring has any remands. It is a light easy to fit motor & quiet.
 

sandytows

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I have been leaning towards the 315 cummins. I don't think I need that much power, but it is a few $ cheaper than the 260MCD cummins which is the engine I really want. My real boggle has to do with the gear ratio. with a 2:1 gear I would need a 29" pitch prop to get 20kts at 2200 rpm. With a 1.5 gear I could use a 22" prop. 1.75 gear would split the difference.
this is with 25% slip that I currently experience at 16kts. I would have less slip at higher speeds as the boat planes off more?

so is it better to spin more pitch slower or less pitch faster?
 

BillD

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25 Terry Jason with Cummins 370 power
I have been leaning towards the 315 cummins. I don't think I need that much power, but it is a few $ cheaper than the 260MCD cummins which is the engine I really want. My real boggle has to do with the gear ratio. with a 2:1 gear I would need a 29" pitch prop to get 20kts at 2200 rpm. With a 1.5 gear I could use a 22" prop. 1.75 gear would split the difference.
this is with 25% slip that I currently experience at 16kts. I would have less slip at higher speeds as the boat planes off more?

so is it better to spin more pitch slower or less pitch faster?

Sandy,

"Rule of thumb" for many DE guys on this forum is "use the largest diameter 4 blade prop" that will fit on the hull and adjust pitch as needed. Wider wheel equals better "bite" of water increasing efficiency.

btw, the 315 Cummins ?? Is it a new engine or RTO ???
 

sandytows

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So after some number crunching and time with a tape measure I have found that none of the aftercooled Cummins will fit in my engine bay which is 32.5" wide. Widening it would require deck work, new engine box cover and widening of rear bulkhead and doors. a lot of work I would rather not undertake. Also out of the question is the 8LV Yanmar.
I am now looking for suggestions.
I have come across the following ideas.
Yanmar 6lp 315 rebuilt
Steyr 286
Other options?
Also while we are talking about this boat.
What are my options to improve cutlass carrier and stuffing box?
Can I use a dripless in my wet keel?
and why is the external cutlass carrier called a dinosaur?
 

BillD

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25 Terry Jason with Cummins 370 power
Can I use a dripless in my wet keel? "Yes"

and why is the external cutlass carrier called a dinosaur? Travis term meaning "old fashion"

Most of the new builds and re-shafting now use a FRP tube and a dripless shaft seal.

My 25 Terry Jason rehab/repower with have a wet tube, 1.75" shaft AND a wet keel.

Lots of previous posts on the topic over the past two years, wet keel, dry keel, tube or no tube.
 

Toolate

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So after some number crunching and time with a tape measure I have found that none of the aftercooled Cummins will fit in my engine bay which is 32.5" wide. Widening it would require deck work, new engine box cover and widening of rear bulkhead and doors. a lot of work I would rather not undertake. Also out of the question is the 8LV Yanmar.
I am now looking for suggestions.
I have come across the following ideas.
Yanmar 6lp 315 rebuilt
Steyr 286
Other options?
Also while we are talking about this boat.
What are my options to improve cutlass carrier and stuffing box?
Can I use a dripless in my wet keel?
and why is the external cutlass carrier called a dinosaur?

(hold on while I put on my flame suit).... How about a GM 350 gas engine? Just paid $8200 for a mercruiser remanufactured engine (only block is old- no emissions requirements) and you could easily get 350hp out of one. You would need a new trans too with numerically higher gears.

What is that Cummins going to cost if you dont mind me asking? (bracing for beating :rolleyes:)
 

sandytows

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(hold on while I put on my flame suit).... How about a GM 350 gas engine? Just paid $8200 for a mercruiser remanufactured engine (only block is old- no emissions requirements) and you could easily get 350hp out of one. You would need a new trans too with numerically higher gears.

What is that Cummins going to cost if you dont mind me asking? (bracing for beating :rolleyes:)

I put 800-1000 hours a year on the boat. when you factor in fuel economy and longevity. a gas engine would be a good example of "pennywise pound foolish"

Cummins QSB305 reman is 28k with no gear
6bta315 reman is 25K no gear
Those are both factry remans with 2yr 2000hr warranties
I could get an aftermarket rebuild6BTA 315 for 16k
BUT
None of those engines will fit in my space without a lot of reworking.

I have found some aftermarket rebuilt 6LPA315s for 14-16k
but I am a little concerned about stepping down to 4.2l displacement from my current 5.9L even though I would see more HP.
for example
6lpa315 max torque is 500ftlbs+/-
QSB 305 max torque is 780ftlbs+/-
6BTA315 max torque is 680ftlbs +/-
 

RyanCT

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How much clearance is needed on the sides? I see the width of engine bay is 32.5" how close to that can you go to shoehorn something in there?
 
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