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Old 02-25-2018, 04:29 PM   #1
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Repower ????

Have spent the last hour searching for similar threads with no luck, so here goes...

(Will also post on AGLCA)...

Have a ‘87 410AC, gasoline powered, that I have spent the last two years “restoring”. Very happy with boat overall. (Since new she has been a freshwater boat. I have obtained the original build sheet and delivery from SeaRay.).

Here’s the puzzle.. I have rebuilt or replaced all that would be considered appropriate except engines. They’ve been serviced and run fine now. This is an issue from the following quandary. We would like to move her to the coast and do the loop. Compression is good on both engines but I do not have actual hours on either engine (gauges replaced B4 my ownership; no records on maintenance.) From the perspective of safety and known reliability on the trip am I better rebuilding these gasoline engines or going all in for a repower with smaller diesels and new tranny’s, etc.? (Currently Mercruiser 454s.)

I’ve looked at many, many boats that have done the loop and everyone seems to be powered by Diesel engines. The obvious efficiency gains are there (and safety w/ respect to fuel type). It’s obviously a no brained on the fuel efficiency benefits.

I own the boat outright; when I starting looking at the resale market there is a lot of fine diesel vessels available but of course they would all come with a mortgage. To sell what I have now would only equate to a down payment on equivalent creature comforts in another boat.

Lately I’ve been thinking that maybe it makes more sense to just keep what I have and repower????

Interested in hearing other’s thoughts and opinions on this.

Thanks!
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Old 02-25-2018, 04:45 PM   #2
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Have not done the Loop, so I can't speak to the best boat for the job, but I have repowered, diesel to diesel. My first thought in your situation, since you like the boat and the engines run fine, is to keep things as-is. Yes you will pay more for fuel and be less efficient, but cost-wise, you'll likely be ahead at the end of the day. The repower you are considering, gas to diesel, will be much more expensive and time consuming than you plan, guaranteed. Worse, much of the cost won't be recoverable when you sell the boat. My $.02 if you must have diesel is buy another boat so powered. Or stay with your status quo.
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Old 02-25-2018, 05:17 PM   #3
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Good advice from Ken.

There are two ways to repower with diesel, and for both of them the numbers just don't add up:

You can put some small diesels in, say a couple of 75 hp Yanmars which will push you fine to hull speed. You will spend close to $75,000 to do so and when you sell the boat you will get zero back and maybe less since small diesels in a big boat are not what the market wants. Fine for doing the loop, but how many buyers have that in mind.

Your new diesels will get maybe 2 mpg at 8 kts. Your old gassers maybe 1 mpg. So if you do the full loop's 6,000 miles you will burn 3,000 gallons of diesel or 6,000 gallons of gasoline. That extra 3,000 gallons would cost you about $10,000, about 15% of the cost of the diesel repower.

The other way to repower is with big diesels, say 380 hp Cummins. These will push you to the same or greater speed as your gassers. But they will cost more than $100,000 to install. You would get more when you sell, but resales usually recoup only half of the new repower cost.

You will probably come out the same as with the small diesels when fuel savings and resale is figured. In other words you will be out $50-60,000.

So my conclusion is if your current gassers have a thousand hours of life left, keep them and do the loop. You will come out ahead.

If your gassers are on their last legs then replace either with short blocks, long blocks or new engines. You probably can do one of the first two for $20,000 total. You still will come out ahead.

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Old 02-25-2018, 05:43 PM   #4
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I've got a twin gasser. A 40' Tollycraft with Mercruiser 454s. The boat a 71 was repowered in 95 with the Mercruiser so they're getting a bit long in the tooth. The stbd engine is showing low compression, about 135. So decision time regarding rebuild or repower or sell the boat as is is not far off.

I've done some rough estimates.

$4K to $8K Overhaul the existing motors
$8.5K replace with new
<$2K short block

With any of the above I keep the fuel system, transmissions, shafts and props.

Diesel repower gueestimates are $60K to $100K. For starters the motors are more expensive. Then comes new transmissions, motor mounts and mods to stringers for same, new shafts, new props and new fuel system. Not to mention all the other bits n pieces I haven't thought of.

Costs for either keep the gas to go diesel will vary greatly on your decisions. One thing for sure is the boat will be a LOT louder and most likely loose it's top end speed.

I'll be hard on the gas and easy on the diesel and say:
$17K for new gassers + a wild guess of $10 labor to remove and install.
$27K to repower with new gassers.

$60K to repower with diesel. I doubt it can be done for that but I'll give diesel the edge.

Wikipedia says the loop is 6000 miles. I think that's statue so I'll covert to nm. 5184 nm.

Recent fuel prices in my area from Active Captain.
Gas $3.95 / gal
Disesl $2.99 / gal

My Tolly at trawler-ish speeds of 9 kts burns 10 GPH
A similar twin disel, just guessing here, 4 GPH

Fun with numbers
5185 / 9 = 576 hrs

Gasser
576 hrs X 10 GPH = 5760 burned X $3.95 = $22,752 fuel costs

Diesel
567hrs X 4 GPH = 1152 burned X $2.99 = $3444 fuel costs

Fuel costs saved $22,752 - $6889 = $15,864

Give the diesel repowered boat 2 GPH, not likely, certainly not with the HP of the Merc 454s and you get a savings of $19,308.

At the cost difference of repower with diesel of $33K. Keep in mind I was hard on the gas repower and easy on the diesel.

Of course that's only part of the answer.
  • Gasser range. Will you be able to comfortably make the longest jump between fuel docks?
  • Gasser safety hazards. Gas is riskier without doubt. But how much riskier? If it were truly high risk all the beer soaked ski boaters around here would be going off like popcorn on summer weekend.
  • Noise. Your main saloon with diesels will be much louder unless you spend big $$$ on sound proofing. The 454s at low speed are barely ticking over, nice and quiet in the saloon.
  • Speed. Low fuel burn diesels won't push your boat near as fast as the Mercs. Not something I'd want to do often but nice when you need it.
I'm not a looper, I'm a PNW boater. When I finally get the boat ready for serious cursing I don't think I'll repower or rebuild unless one or both are near failure. I'll install new plugs, new plug wires and other related bits n pieces. Take her out for a local cruise and run her hard and hot to see how she holds up. If she behaves herself off I go!


At the fuel dock(s) when crying over the cost I'll remind myself I paid peanuts for the boat compared to something like my buddy's KK42.


If / when the engines become unreliable I'll sell her for pennies on the dollar and walk away content I had some affordable boating behind me.



Of course this is all just one person's opinion and others here will surely disagree.
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Old 02-25-2018, 05:44 PM   #5
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There are a lot of uniflite 42 gas powered boats that can be picked up cheap. Uniflite built all their 42’s to take diesel even if they were sold with gas. This means the uniflites already had the space, the shafts were already big enough, there was already room for the correct prop, the fuel tanks already had the correct plumbing, and the exhaust was all ready the correct size.

YET!!! I could never make the numbers work. I tried the numbers with new yanmars, with old dd671s, with marinized gm 6.5L, with hino’s from Bayliner, with D6 and D4 from Volvo, with John deer take outs. The closest I got was when I was offered a pair of old Volvo take out engines (for free) but then the over haul cost of old volvo’s Killed the project.

It was always easier and cheaper to just buy a different boat that had the correct engine.

One thing about gas. It’s quieter, stinks less, and you can always find some one who can fix it. Plus a drop in new engine is only $15,000 or a long block can be had for $4,000. Gas hurts at the pump but it won’t break the bank.

If the boat is right keep the gas. If it’s wrong sell and start over.
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Old 02-25-2018, 05:46 PM   #6
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I see Ken and djmarchand replied while I was typing. Obviously I agree with both. Dance with the girl you brung....
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Old 02-25-2018, 06:11 PM   #7
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tiltrider is the only one to mention it but I think the lighter weight, smoothness and vastly quieter personality is shuch a draw a case could be made (David did a good job of that I think) to stay w gasoline. The only real draw w diesel is low fuel burn and longevity.

In a way the gas engine may still be the best engine for pleasure boats. The real reason most trawlers have diesel is their commercial like low rpm big fishboat sound. I’ve said supportive things about smaller diesels or gas engines many times on TF and the feedback that always accompanies those comments is about the “screaming” sound. The low rpm diesel is like good ambiance in a resturant. And the skipper gets a bit more hair on their chest and viewed as more of an old salt. At the minimum this thread shows little or none of that. That puts a smile on my face.

IMO you (the poster) don’t need any rebuilds or repower jobs. Just belts, hoses, pumps, and perhaps re-torquing the heads and all the rest. Through inspection of exhaust and related things. Then some time on the engines to make sure you did things right and all is ready for the long run.

In your shoes I’d just keep running that boat with her gas engines with good maintenance, good warmups and cooldowns before shutdowns.
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Old 02-25-2018, 06:48 PM   #8
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There may be yet another option........
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Old 02-25-2018, 07:22 PM   #9
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I repowered diesel for diesel. The trigger was that I had to replace fuel tanks, which entailed removing the engines. The old Cummins 555 started easily, ran well, reached WOT and only had 1950 hours in 31 years. They were started often, but only did short runs apart from one trip to Alaska from Seattle. How much longer would they last? No idea. Parts availability for them in Australia was a big question mark as well. Going over both motors for external items was going to cost almost as much as one new John Deere.

So in went two new JD's. Very happy with the outcome. I don't think it added much value to the boat, but it would have increased market appeal and saleability. As does the new fuel tanks. Only worth doing if its a boat that you will keep a long time. Otherwise, keep the old engines going!
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Old 02-25-2018, 07:28 PM   #10
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If you repower with lighter engines will the boat now roll in an unsafe or unpleseant manner due to the altered center of gravity?
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Old 02-25-2018, 07:34 PM   #11
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Quote:
Originally Posted by Benthic2 View Post
There may be yet another option........
LOL. Hasn’t thought of THAT option. :-)

Once again the members of TF come through with objective, thoughtful responses.

Today was my first day back on “the lake”. Spent a week down in the SRQ area visiting some boating friends and of course there were plenty of boats to look at, beers to drink (bourbons after sunset!) and grand ideas thrown about. Whilst in FL came to the conclusion it made for sense to move the boat I have to the coast. Sitting on her today enjoying some fine weather the repower thought came to me as though it were a great epiphany. Started up TF to see if anyone else had similar thoughts (after reading the responses, crazy idea!)

I appreciate the candor and time you’all took to respond with not just opinion but some serious brain matter applied.

In the end I can see where the most economical choice is to continue to burn gasoline As it was said, dance with the gal you brought!

Thanks everyone. Great discussion.
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Old 02-25-2018, 08:00 PM   #12
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After going the new long block route on an old gas engine, I would go 2 new complete engines. The point being the old accessories will fail piecemeal along the loop and drive you nuts. With new complete engines you reduce that probability to nil and you will still have usable engines after completing the loop. With long blocks you dramatically increase the mechanic labor hours to put the whole thing together.
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Old 02-25-2018, 08:48 PM   #13
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At the risk of hijacking the thread....

Nomad Willy
Quote:
In a way the gas engine may still be the best engine for pleasure boats.
I'm coming to the same conclusion. A huge advantage of the old skool diesels is once you get 'em started they'll get you home. All they need is fuel and air. No electricity required, no electronics. Most of the newer environmentally friendly diesels are entirely dependent upon electricity and electronics which was the big weak point of gasoline engines. Now that new builds require tier III with all their computers the lighter weight, quieter, smoother, less expensive gasoline engine and their computers may make more sense.

The two remaining advantages to diesel are safety, gas can't beat that. And longevity. Longevity only comes into play if you put a lot of hours on for a lot of years. Most recreational boaters do not.
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Old 02-25-2018, 10:27 PM   #14
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Portage Bay,
I’ve only had one engine failure and the problem was fuel. And I’ve read most diesel engine failures are a result of fuel issues. So “once you get them started” theory can go south. I thought everything was perfect on my engine and the installation. But the mechanic that did most of the install used way too much fuel line thread sealant and at times the floating debris got in the small holes and impeeded the flow until finally it shut off the fuel, .. and engine. Of course we were several miles out into Georgia Strait. I completely reworked the fuel system w new hoses, clamps and did considerable replumbing. Eliminated a lot of unnecessary parts and made things simpler.

But now I wonder what other problem lurks ready to fall on me. Thought everything was super good to go before. All we can do is our best or hire someone to check your work or do it ourself.
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Old 02-25-2018, 10:43 PM   #15
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Nomad Willy,

Yes fuel problems can kill a running diesel of any vintage. I should have phrased my post better. Electrical / electronic problems won't kill an old skool diesel.
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Old 02-25-2018, 11:20 PM   #16
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Quote:
Originally Posted by Portage_Bay View Post

At the fuel dock(s) when crying over the cost I'll remind myself I paid peanuts for the boat compared to something like my buddy's KK42.

If / when the engines become unreliable I'll sell her for pennies on the dollar and walk away content I had some affordable boating behind me.

Of course this is all just one person's opinion and others here will surely disagree.
This was one of the "justifications" I made to myself when she was first purchased - "I'll remind myself I paid peanuts for the boat compared to something like my buddy's KK42."

The idea of repower entered my mind due to a.) unknowns associated with the maintenance history before my ownership, and b.) that unknown equating to what kind of reliability while XXX miles from home. That [cost] of knowledge and peace of mind equating to the $$$ spent on a rebuild, etc.

I've got time to weed through the best options, and the input received has been outstanding. If I were to do anything (all hoses, belts, impellers, plugs, caps, rotors, wires, pumps, etc., have been changed), it would be new compression tests and determine how the top end(s) are holding up.

I believe the range of the boat as powered currently is right at the edge of being sufficient for the longest leg on the Mississippi at "trawler" speed (with the need to factor in reserves as well).

At 8-9kts, I am getting a little better that 1.0 mpg per engine (3.5 gph x2 eng). 200g fuel x 2 tanks /XX% reserve... I know we would need additional fuel for that 450 mi "gasoline" leg if we don't do the Tennessee-Tombigbee route (this alone may make the decision easy). My overall "trawler speed" range is only about 375 mi. (My estimates being based on ~15% fuel reserve. Is that too low a % for reserve?)

My extended travel experiences in the salty stuff has all been via sail. (Northern Caribbean out of Dinner Key, FL; 42' Catalina). To me this planning is just another equation to solve and your collective input has been very helpful and appreciated.
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Old 02-25-2018, 11:22 PM   #17
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Quote:
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After going the new long block route on an old gas engine, I would go 2 new complete engines. The point being the old accessories will fail piecemeal along the loop and drive you nuts. With new complete engines you reduce that probability to nil and you will still have usable engines after completing the loop. With long blocks you dramatically increase the mechanic labor hours to put the whole thing together.
Thats been the concern . . . and likely conclusion to this chapter.
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Old 02-26-2018, 07:44 AM   #18
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Another hint to increase gasser range is to run on one engine at hull speed. Make sure your gears can handle the windmilling and swap motors say once an hour.

Gas engine efficiency is horrible down at low load. The engine in use will be at higher load and probably get you like a third greater range. A 454 burns like 1-1.5gph just to idle. You get some advantage running a twin diesel boat on single, but not near the advantage you'll see with gassers.

454's are very durable machines. Do the basics: New sea water pump, belts, fresh ignition stuff, check hoses, make sure manifolds are good, good fuel filters, fresh fluids, fresh gear coolers, etc. Then take it for a day trip around home port and beat on it a bit. No failures, you are as loop ready as you can get.
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Old 02-26-2018, 07:56 AM   #19
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Quote:
Originally Posted by texasnielsen View Post
Here’s the puzzle.. I have rebuilt or replaced all that would be considered appropriate except engines. They’ve been serviced and run fine now. This is an issue from the following quandary. We would like to move her to the coast and do the loop. Compression is good on both engines but I do not have actual hours on either engine (gauges replaced B4 my ownership; no records on maintenance.) From the perspective of safety and known reliability on the trip am I better rebuilding these gasoline engines or going all in for a repower with smaller diesels and new tranny’s, etc.? (Currently Mercruiser 454s.)

Lately I’ve been thinking that maybe it makes more sense to just keep what I have and repower????

Just another data point...

A previous boat neighbor with a mid-80s Bertram 35 convertible blew a gas engine, so decided to repower with Cummins B diesels. Counting the new diesel genset too (and some unrelated upgrades to his head, dunno details), his cost was about $100K. Last I heard, the boat was for sale, listed at about $125K.

OTOH, he was very pleased with the improved performance. (His subsequent intent to sell wasn't about the boat or engines; just that he'd later bought a home in FL somewhere up a canal and wanted to switch to a boat with lower air draft so he could keep it at his new home.)

You could perhaps calculate Loop fuel burn with present engines versus predicted fuel burn with diesels... and compare cost of diesel repower versus savings in fuel.

Another option might be to repower with newer more modern gas engines, assuming there are any useful candidates. Maybe only when you really must either do a major rebuild or repower. The same kind of cost/savings comparison could be useful...

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Old 02-26-2018, 08:12 AM   #20
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Why not just add fuel injection to your existing motors?
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