Tartan 34c Engine Repower / Replacement

Monohull Sailboats

Repower Specifications

LOA: 34.42’
LWL: 25'
DISPLACEMENT: 11,200 lbs
BUILDER: Tartan Marine


A Sparkman & Stevens design, built by Tartan Marine.  This boat has provided many an owner both cruising and racing pleasures. Unencumbered by shallow water, plenty of Tartan 34C’s will be found on the east coast.  Still favored by owners after more than 40 years, this is a model that consistently sees Beta repowers year after year.


The factory installed engine was the Atomic-4, which has a realistic power rating of approximately 18 hp and did not use a reduction gear.  The propeller size was limited to a small diameter, 2 or 3 blade. The ability to push the Tartan 34c powered with the Atomic-4 into weather or a head sea was very limited.

Repower Recommendations

The Beta 25 A4 Replacement has proven time and again to be the best choice of power for this vessel. Many owners have found that it produces the power they need for motoring and low speed handling, while also providing excellent efficiency. The Beta 25 fits the Tartan 34C engine box with minimal or even no modification required. The Beta Marine Atomic-4 replacement mounts, with 11.5” wide spacing, will match the original Atomic-4 spacing and allow for an easy fit.

Repower Recommendations

The Beta 25 will be 50 lbs lighter than the original Atomic-4 and more compact.

Due to the limit in propeller diameter, the 2:1 ratio gear is best suited for this installation.
A three blade propeller will give the best performance and efficiency.

Installation Considerations


Propeller size for the Tartan 34c is limited to 12” with a fixed propeller. A feathering propeller with an extended hub may allow a 13” diameter propeller to be installed.

The Tartan 34c has a unique exhaust system that utilizes a custom stainless steel riser. Replacement risers that are correctly sized for use with a diesel engine are available.

The Beta exhaust is available as a dry threaded stub. This will allow easy connection to a riser using a flexible stainless steel hose, which is also available from Beta Marine.

Other Resources

The Tartan 34  is common boat repowered with Beta Marine diesel engines. We have engine replacement experience with this model and we have pictures, drawings and measurements for reference as well. Contact us to discuss your boat in more detail, or add to our forum discussion on this specific boat model through the link below.

Tartan 34c Repower – Forum Discussion

Sailing Magazine Story on the Tartan 34


Customer Testimonial:

A Beta customer repowered his Tartan 34c with the Beta 25 and offers the following conclusion.

After having used the boat three months this summer, I am
very satisfied with the result. The engine and propeller
provide the thrust to navigate safely in choppy waters.

One important benefit is that the boat can be stopped
quicker and has good backup power. It is reassuring when
approaching a dock too quickly.

It is a worthwhile upgrade. The T34C sails well either
under sails or under engine power”.



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