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Lets talk Diesel engines

Old 06-09-2021, 03:21 PM
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Remove the inboards. Close the transom. Install outboard power.

You won't be the first. You won't be the last.

Knowing that you will thank me once the job is done, you are welcome.
Old 06-09-2021, 03:28 PM
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good for you for trying to think outside the box while also picking up new knowledge & skills and ending up with something that to this point you've only dreamed of.

now, with that said, this is going to cost a lot of money to do even marginally right and you've made it very clear there's no way you can afford it. no harm in challenging what I'm saying (and everyone else is saying as well). but, you can't afford it and you're going to figure it out sooner or later. and the sooner you figure it out the better off your wallet will be.
Old 06-09-2021, 03:34 PM
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Originally Posted by Greymare View Post
As for the whole sell the boat and buy one with diesels. I am not sure if you read the part that I don't have 42' boat money over here. I got this boat for a steal at an auction is the only reason I could afford it
The thing about this, though, is that going from Crusaders to diesel propulsion is not a repower. It's a complete refit.
Old 06-09-2021, 03:41 PM
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Originally Posted by alloyboy View Post
Remove the inboards. Close the transom. Install outboard power.

You won't be the first. You won't be the last.

Knowing that you will thank me once the job is done, you are welcome.
It's an old 42 ft heavy ass Sportboat!
It will need 100 k worth of outboards to move it at a decent speed and it will be a total abortion
Doubt anyone will be thanking you
Old 06-09-2021, 03:49 PM
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You should start out doing some research on causes of boat fires and accidents. Gasoline fumes exploding is not the most common cause of injuries or deaths. Alcohol use and inattention certainly are much bigger dangers, drowning kills more people. There are an enormous amount of old and poorly maintained gas boats on the water, a lot of careless refueling, and still fuel fires are rare.

The first thing I did on my boat was replace the fuel lines with modern rubber lines properly secured, install proper marine fuel pumps and carbs, verify my filters, bonding, vents, and vent blowers and tubes were in good shape. I follow all the recommended procedures when refueling, don't rush anything.

https://www.boatus.com/expert-advice...rd-fire-claims

https://www.uscgboating.org/library/...stics-2019.pdf
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Old 06-09-2021, 04:07 PM
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Modern diesels are tending towards high HP and light weight out of smaller displacement which means you can have reliability issues even before factoring in all the ECU issues. Not time bombs but nothing like the older generation in terms of lifetime.
My money would be on two rebuilt 3208s @ 375hp. Even with it's flatter stern deadrise it will never be a 40kt boat unless you put 150k of outboards on the back or 700hp diesels in place of those rustbuckets.
Old 06-09-2021, 04:24 PM
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Lots for you to think about. First off you have plenty of room to install a set of diesels. It will be lots of work and you have to consider a number of things. Lets say you go with a set of Cummins. You will need a new exhaust system of 6" diameter hose along with mufflers. New fuel system with return lines to the tanks. Maybe new struts (unless the originals can be bored out) to handle larger diameter shafts along with new props. Engine bed mods, enlarged water intakes etc. Could be like a new boat when done. You should be able to find a set of Cummins 6BTs at 330hp with gears for a good price. I would suggest 2 to 1 reductions. You don't need 450 hp IMHO, unless you need a rocket ship. Twin 330s should give you much improved performance over the gassers. Good luck, I am subscribed. PM me if you need any more input.
Old 06-09-2021, 04:25 PM
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Agree with everyone above…this will be a way bigger and way more expensive swap to make than you think. Whatever you think in terms of time and dollars, double that and add another 50% and you might be in the same zip code.
Also agree with the safety issues of gas engines…you rarely see gas boats blow up especially if the owner is a responsible and conscientious boater.
Your words…great running pair of Crusaders. I’m old school…if it ain’t broke, don’t fix it.
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Old 06-09-2021, 04:51 PM
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Also check the casting numbers on the heads those engines might be worth a good bit if you do change
Old 06-09-2021, 05:15 PM
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If you start with a 42’ Post gasser . Let’s say $25k . Do the swap . I think it could be done for $150k on your blood and sweat. You just made a boat that would be hard to sell for $100k.
Old 06-09-2021, 06:36 PM
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Originally Posted by HarborRd View Post
As far as engines go, I have heard Detroit 2 stroke parts are becoming hard to source....others can reinforce or refute that.
Jimmy diesel parts are not hard to source. Been working on and running them for over 40 years. We got a pair of 12V71's and I wouldn't trade them for any other engine on the water. Series 71's are completely mechanical engines and are one of the cheapest and most reliable diesels you can own. But reality is that dropping 7,000 lbs worth of a pair of 318's in the hole where Crusaders came from probably isn't going happen. If it were possible you could maybe rig up a v-belt and clutch arrangement to use one of those Crusaders for a pony motor to turn 'em over though.
Old 06-09-2021, 07:31 PM
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mechanical diesels RULE !

I did mine 16 years ago and never looked back

Could not do this today - costs are NOT the same

My swap was relatively easy, plus the genny was already a diesel

get ready for a lot of "AS LONG AS I'M IN THERE, MAY AS WELL ...."

RWS

Old 06-09-2021, 09:02 PM
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I had MTU's in my last big boat, got my parts at Freightliner in Anaheim, without the "Marine Mark up!" Same with Detroit, you can get most of those parts at Freightliner. Also, We have Quinn Cat Power out here as a Cat supplier for the truck and heavy equipment side in So Cal. I'm sure you have the same available to you where ever you are, if parts is the issue holding you back. Just an FYI.
Old 06-09-2021, 09:38 PM
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Pay attention to what noelm said in post #17. Diesels turn considerably lower rpms than gassers which means that to achieve similar thrust you're going to have to swing bigger propellers which may require larger diameter shafts than you currently have. I think a wise first step would be to consult an expert who is familiar with what changes would need to be made to reach your goal. Perhaps a marine surveyor, engineer or someone in a shop that does a lot of conversions. As others have stated it's a complete re-rigging not just a simple repowering project, let that concept sink in. You may well be up to successfully meeting the challenge, but I think you'll also be a lot happier working on it if you know what is needed before you get into it rather than learning through a series of unforeseen surprises.
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Old 06-09-2021, 09:49 PM
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Originally Posted by flcatcher1 View Post
Pay attention to what noelm said in post #17. Diesels turn considerably lower rpms than gassers which means that to achieve similar thrust you're going to have to swing bigger propellers which may require larger diameter shafts than you currently have.
Will there be room behind the struts for larger props that don't come too close to the hull? Might need struts that put the props further back, but then the rudders are there.
Old 06-10-2021, 01:04 AM
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I have a friend who did this to a smaller boat. 28’ Topaz. It came with 351 Ford gas burners. He gutted it and installed 4 cyl Yanmars with all necessary running gear and conversions. Engines were new @ $30K each. Entire project was $120 K. This was 20 years ago. Did most of the work himself. Performance and fuel economy was amazing for the time period. 40 kt top speed 30kt cruise. Really should have worn ear protection to ride in that thing though!!
Old 06-10-2021, 04:02 AM
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Originally Posted by Xaddo View Post
I have a friend who did this to a smaller boat. 28’ Topaz. It came with 351 Ford gas burners. He gutted it and installed 4 cyl Yanmars with all necessary running gear and conversions. Engines were new @ $30K each. Entire project was $120 K. This was 20 years ago. Did most of the work himself. Performance and fuel economy was amazing for the time period. 40 kt top speed 30kt cruise. Really should have worn ear protection to ride in that thing though!!
+ 100

Did mine 16 years ago

My project was less as I did a great deal of the work, including removal of the 454 Crusader gassers

amazing fuel economy, increased range and my optimal cruise went from 13-15 kts to 19-22 kts

Engine noise was negated as we added a layer of SOUNDOWN insulation to the cockpit floor, the new turbo whine is a sweet sound and is muffled

completely changed the character of this vessel.

RWS
Old 06-10-2021, 04:33 AM
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Duramax Marine Diesel Replacement


Peninsular Diesel
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Old 06-10-2021, 05:04 AM
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I think you left out cutting bigger holes in the transom for the exhaust and re-engineering the exhaust.
Old 06-10-2021, 06:09 AM
  #40  
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Default Don’t do this.

I still have nightmares about replacing the 454s an Egg Harbor 36 with Cummins diesels in 1990. If you undertake this, you will spend not a penny less than $100,000 and a lot of blood by the time that all fuel, electrical, exhaust, controls, shafts, props, cutlass bearings, bonding, engine mounts, blowers, air intakes, fiberglass and other work is done. New prop cost will range between $5K and $15K.

It hasn’t gotten any cheaper either. In 2017, I replaced two 8V92s in another boat with CAT C12.9s. Today's prices for parts, hoses, fittings, controls, wiring, gaskets, exhausts and other parts are staggering.


Last edited by LKD; 06-10-2021 at 06:14 AM.

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