How difficult to convert this engine to variable speed?

[Homefront]

I found this 13.5 hp Yanmar at what seems to be a great price, but the descriptive says it's set up for constant speed. Can this be easily changed to a variable throttle?

https://www.surpluscenter.com/item.a...atname=engines

[TeddyDiver]

Throw the governor overboard and set a manual instead from another engine. Not a big deal..

[Homefront]

That's good to hear. Thanks.

[gonzo]

All diesels have a governor. If you throw it overboard, it will run wild. You need to connect the throttle to the governor.

[apex1]

Teddy meant to replace the "fixed" one by another, not only to throw the gov.!

Obviously that was half the part of a generator plant set at 3600 rpm means 60hz. And the 160 pieces they have in stock, let me assume a deal got shot.

Take care homefront, there is a lot of stuff to buy to make that a functional boat engine, you know!?!

Regards
Richard

[gonzo]

Many engines use the same governor. In a generator setup, it is fixed. Usually with a short adjustable rod or screw.

[TeddyDiver]

Originally Posted by gonzo

All diesels have a governor.

This might be a kind of "not-speaking-with-common-terms-thinghie" , but I'm used to gasoline engines having a governor and diesels instead having an injection pump. So in this regard I do mean the governor being the "thinghie" controlling the pump.
Best to get a cataloque/manual to see the right parts.

[CDK]

This is an excellent engine for a small boat. As Apex1 wrote, it was configured to power a generator, which means two things.

The throttle lever mechanism (completely external) has the adjustment screw set at 3600 rpm for 60 Hz operation. It can be adjusted with a screwdriver.

The spring length and diameter which determines the governor characteristics (also external) is chosen to give precise load control between 3000 and 3600 rpm. In the range between idle and 3000 rpm it is less efficient, so the engine behaves more like a gasoline engine. For a boat that should be no problem.

[gonzo]

Gas engines are controlled completely differently from diesels. There are gas engines with governors to keep a constant speed. Diesels, unless electronically controlled, use a centrifugal governor. It is spring loaded and the tension of this spring against the centrifugal force of the counterweights spinning balances at a certain point. That is the RPM the engine will run at. In a generator, the spring tension is fixed. For other applications, the spring is connected to a cable or lever to which can be adjusted manually.

[Homefront]

Gentlemen,

Thank you all for the replies.
I'll bare my soul and tell you what I have in mind for this engine and would appreciate any thoughts..
I fish the waters around the NJ coast, for blues, stripers, flounder, etc. I have a small skiff for back bay and river fishing, and my friend has a 20' deep-V that we use for coastal.
I'm tired of pounding, tired of bad slow-speed behavior, tired of noise, tired of big fuel bills.
I'm also the one who encourages us to go out when the water is a less than comfortable 3-5'; we've had waves roll over the foredeck and up the windshield more than once when fighting back to the dock at 5 or 6 knots, against the wind.
I want a boat with a 2-person pilot house, as well as a dodger for gear and a portable toilet, and a self draining deck sole.
I'm considering the Atkin Sallie Hyde http://www.boat-links.com/Atkinco/Ut...allieHyde.html, http://www.boat-links.com/Atkinco/Ph...yde/index.html and I might arrange things sort of but not exactly, like this:

[Homefront]

As to the engine, what are your thoughts on alternator, exhaust, cooling, transmission, propeller selection?
I'm fishing for things I don't know or may not have occurred to me .

[gonzo]

All those parts should be standard. They are plenty of those engines around. The original transmissions, are a Japanese built Hurth. You may find a US made transmission for cheaper.

[apex1]

Are you planning to put the Yanmar into this (beautiful) Atkin design?
That engine has not enough "beef" to propel such boat uphill!

[Homefront]

That's the idea.
Atkin recommends a 12 hp slow-speed engine. You think this high-speed unit would be insufficient, regardless of propeller choice?

[apex1]

You gave the answer already! Prop choice!

These wonderful boats are heavy and turn relatively big props. You need some torque (displacement) to turn them.
You will have some 8 horses (just guessing) left at the prop, when your done with the setup. Assuming you set her at 3000rpm max. to have at least some years of service life, not weeks. But there is not much torque to turn a big wheel.
Atkins recommended that due to the fact that these engines were displ. monsters at 1,5 or 6 even 10 liter.
This little Jap is the opposite at just 0,57 liter, though a fine engine, no doubt.

Maybe we can compensate a bit by using a high ratio gearbox. But would´nt it get cheaper to find a Sabb or Lister Petter with all the gear, second hand?

Sorry I´m not happy to have rained on your parade, but I think better the bad news now than later when all the stuff is bought.

Regards
Richard