Under powered trawler ????

Hi all, new member with out a vessel yet here

My buying adventure is hovering over a 45' Sea Ranger sundeck.

Aprox. 40K lbs. powered by twin Lehman 135's .

I love the affordability of the lehmans and have no need to go fast.

Seller's agent reports 7-8 knot cruise.

Will this boat just cruise at displacement speed, or actually plane ??

Enough power to motor against tide surge ?

Thanks all for any help. I am flying out to SD from Chicago to see the boat

(and several others) next week. Thanks, Marty

They are very popular engines.

Best to avoid the theoretical numbers on speed. Displacement cruising speed could best be defined as the maximum speed a boat can go with modest fuel consumption. Beyond that point, it requires a substantial increase in fuel consumption for a modest gain in speed. My guess is that the listed cruise speed is about as fast as you will go with modest fuel consumption. Would expect rhat the boat could do 9+ knots for a substantial increase in fuel. Not familiar with the hull shape of this boat, but doubt there is any chance of a 40K boat planning with 270 HP.

Ted

Mpgjr

I would say the set up that you mentioned in your question portraits a displacement situation. Therefore, those engines will never plane a 40klbs boat with a probable 40' LWL. It is a slow economical and reliable trawler set up, for sure.

Just check if the boat is in good conditions.

O C Diver said:

Best to avoid the theoretical numbers on speed. Displacement cruising speed could best be defined as the maximum speed a boat can go with modest fuel consumption. Beyond that point, it requires a substantial increase in fuel consumption for a modest gain in speed. My guess is that the listed cruise speed is about as fast as you will go with modest fuel consumption. Would expect rhat the boat could do 9+ knots for a substantial increase in fuel. Not familiar with the hull shape of this boat, but doubt there is any chance of a 40K boat planning with 270 HP.

Ted

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Ditto

Looks like nice boats, with good room and well equipted. Whcih one are you looking at the dark one or the light one, as i see two on Yachtworld?

max speed will be 10 knots and the engines, at least at lest for these two boats are the SP120s, not the 135.

Richard

mpgjr said:

Hi all, new member with out a vessel yet here

My buying adventure is hovering over a 45' Sea Ranger sundeck.

Aprox. 40K lbs. powered by twin Lehman 135's .

I love the affordability of the lehmans and have no need to go fast.

Seller's agent reports 7-8 knot cruise.

Will this boat just cruise at displacement speed, or actually plane ??

Enough power to motor against tide surge ?

Thanks all for any help. I am flying out to SD from Chicago to see the boat

(and several others) next week. Thanks, Marty

Click to expand...

Boat Diesel Power Calculator says if your water line is 41', an average semi displacement vessel, at your displacement, hull speed is 12.8 knots and will require 264 hp. To cruise 8 knots you'll be using ~64 hp.

With a 41' LWL the theoretical hull speed [1.34*sqrt(LWL)] is about 8.6 kts. The most economical cruise speed should be somewhere between 6.5 and 7.5 kts. With that much horsepower, and a semi-displacement hull, the boat is almost certainly capable of exceeding its theoretical hull speed--at the cost of greatly increased fuel consumption, of course.

Thank you all for your help. Us newbies chime in with questions that could probably be found in an archive , but still get answered, so thanks again.

I will offer more once I get out and actually see the boat. There are several prospective buyers according to the broker so I will be short on info for another week or two

Economical, reliable, long lived.no turbo.... It sure seems like Lehman's are a good choice. What are the "cons" ?

mpgjr said:

There are several prospective buyers according to the broker...

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There are ALWAYS several other prospects, according to the brokers. This is a sales technique that is as old as time. They want to pressure you into making a quick decision, and a quick offer. There is also the very well known (at least, amongst salesmen) human characteristic of finding something more desirable if you believe that others find it desirable.

Don't fall for it. Even if it is true, there are lots of boats out there, and you will be better off taking whatever time you need, and finding the right boat for you at the right price, than you will be hurrying your decision on this one.

Good luck.

I once looked at a Sea Ranger 47. Made by C&L, on the same hull as my C&L44, just lengthened. Likely your 45 is the same hull.
I have 400 total hp. I can get to 10.5 knots, at WOT, but the hole at the stern is deep. To get up on a plane, I would need to at least double hp to 800, but I don't plan on trying it.
Your 40k is light for that hull, so probably without fuel and water. I carry 600 gal (US sized) and 300 of water, and my total weight (weighed on a travel lift) is 44k. add a foot, load appropriately and yours will be 45k.
With only 270 total hp you will cruise at 7.5 to 8.5 on 4 to 5 gph with a max at 9.5 but you won't like the fuel consumption to do 9.5 so wont do it.