Hello! I'm building a Titan in steel.

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Hello! I'm building a Titan in steel.

Post by mrtom » Mon Sep 14, 2015 12:50 pm

Hello all!

I am new to the forum and this will be my first scratch-built boat. The metalworking skills are not an issue for me as I am a professional metal worker. I have many questions about other aspects of construction - particularly the motor installation.
The Titan is rated to have up to a 50 HP motor, however I already have a VW AAZ 1.9l mechanically injected turbo diesel that I was planning on marinizing. I want to use this motor because I already own it, it runs well and is easy to get parts for.

Could someone with more knowledge in this area point me in the right direction in terms of how this will affect my build or what my options are for propeller pitch and sizing, if I were to use this motor?

I was thinking that sinceit is diesel, it should only burn fuel in accordance with the power it is displacing through the hull. Am I on target with this assumption or will I be burning much more fuel?

My next question would be what gear ratio would be appropriate? A friend of mine has a marine hydraulic transmission that he believes is from a gas motor installation and is 1:1 ratio. Would I be able to use this in any way for my boat?

Any help would be welcome and appreciated.

BTW. I have the inboard motor installations book coming in the mail.

Thank you,

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Re: Hello! I'm building a Titan in steel.

Post by steveh41 » Mon Sep 14, 2015 1:57 pm

My suggestion for determining prop size and pitch, gear ratio etc. would be to obtain a basic membership on boatdiesel.com and use their prop size/gear ratio calculator. You will need to input hull info such as length, weight and type of hull (displacement vs. planing etc.), as well as engine rpm and power at cruise. The program will give you a best estimate for the correct prop and gear ratio for your setup.

When you are ready to buy a prop, the vendor will assist you in fine tuning what you need and make a recommendation for an appropriate shaft.

As far as fuel burn goes, 20 hp is about 1 gph for diesels so you can estimate fuel burn at different cruise speeds using the required hp for that speed ( also from calculator).

Sounds like a great project; be sure to post some pics!


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Re: Hello! I'm building a Titan in steel.

Post by gap998 » Mon Sep 14, 2015 2:33 pm

I don't about US suppliers, but Lancing Marine in the UK supply marinising kits & parts for this engine, and they may be able to offer advice on prop & gearbox suitability: -


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Re: Hello! I'm building a Titan in steel.

Post by Cool Runnings » Mon Sep 14, 2015 11:20 pm

Hello there Tom-Congratulations on selecting a Titan as your first build. It is a very fine design.

We have just finished ours recently and it is a terrific vessel. You may have seen some information and pictures on the forum already(Mid Year Titan)
There is another chap on the forum(El Jefe) who has started a build in steel as well, but have not heard from him in a while.

Some information that may be of use from my end. We have the extended version of 21ft 6in,of which the base material is in aluminium.
Regardless of the material used ,the designed displacement should still come out the same.
The engine used in our case is a 1.2 litre 30HP variant of a Kubota diesel with a 2:1 reduction gearbox . Prop used is a 14 by 9 RH throw on an 1 1/8in shaft.
My conclusion is that the package we used is right for the boat and even a slightly smaller engine of 20-25HP range would have sufficed. She gets up to 6.5 knots quite easily and has no trouble punching into a seaway without too much loss of speed.

Some things to consider is that a displacement hull has a theoretical hull speed calculated on it base length etc. If a larger than required engine is utilised there will not be any real gain as the tail of the boat will probably bury down. The end result under full power is that more fuel gets unnecessary burnt and not a lot of additional hull speed will be gained.
The VW engine you have already may work just fine with the right engineering, but some research will be warranted.
As with any engine they do like to be placed under a reasonable load to prevent problems such as cylinder bore glazing etc.

If Doug(Slug) is around on the forum, he may have some suggestions for you. I believe he is on a road trip at present.

Best of luck and look forward to your progress.


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Re: Hello! I'm building a Titan in steel.

Post by mrtom » Tue Sep 15, 2015 5:33 am

Thank you all for the replies. All of these ideas are excellent. I did fail to mention that the BHP of that engine is rated at 75. I will try the calculators mentioned. It sounds like a great resource. And the fact that there are marinizing kits available is good news as well. It is not set in stone that I will use this engine just yet. I have my eyes open for other options.

I will post pictures when I get that far. I am at a bit of a stand-still on beginning the boat. I have drawn all of the ribs and keel - stem to stern-post - in autoCAD and am having those parts NC plasma cut at the shop where I work. The delay is that the full paying customer jobs take priority and this has been a setback for a couple months now. Work is slowing down some and they should be cut very soon.

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Re: Hello! I'm building a Titan in steel.

Post by mrtom » Wed Sep 16, 2015 8:13 am

Cool Runnings wrote:You may have seen some information and pictures on the forum already(Mid Year Titan)
I took a look at your boat and it is certainly impressive work! I love the vent funnels above the forward berth! I know there is a proper name for them, but can't think of it at the moment. I will certainly be referring to your work when it comes time to do the wooden portion of my own.
The choice of her name is perfect too!

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