Pearson 10M Engine
The 10M came with several differnet engine installations. Most seem to be powered by the Atomic Four gas engine with a direct drive transmission. According to the BUC price guide diesels were optional with a Faryman 25hp in 75 (I have seen a '74 with this engine), a Westerbeake 20hp diesel in 76. the Faryman again in 77, and a Volvo 23hp (MD11) from 78-80. The volvo MD11 in my 78 10M has a v-drive after the transmission with the output shaft of the engine facing forward and the prop (left handed) located about 3 feet forward of the rudder skeg. The Atomic 4 and the Faryman I saw have the output shaft facing aft and the prop was about 1 foot in front of the skeg.

Engine Projects Page
Typical Atomic 4 Installation (1974)
Typical Farymann Installation (1974)
Typical Volvo Installation (1978)
V-Drive Installation on Volvo MD11C (1978)
Stuffing box on Volvo MD11 Installation(1978)
Volvo MD11C Drawing from Engine Manual
V-Drive info on the 422 web site technical info page
Propeller page
Drawing of propeller clearance

Pearson 10M's with the Volvo MD11C were equipped with a Walter v-drive reduction gear (2:1). The engine is mounted with the shaft exiting forward and the v-drive redirects it aft under the engine to the shaft log. The Walter Maching Co. is still available for technical support and has rebuild kits for the v-drive.
    The Walter Maching Co. Inc.
    84 Cambridge Ave.
    Jersey City, NJ
    201-656-0318 Fax
V-Drive Installation on Volvo MD11C (1978)

    Farymann Parts
    Farymann Diesel U.S.A.
    870 Route 530
    Whiting, N.J. 08759
    Email farymann@farymann.com

Atomic 4
I don't know much about the A4 but there are several sites with a lot of information. It would be silly for me to try and duplicate these excellent web rosources here so follow the links below.

Atomic 4 Info Sites
Ron Davis'A4 info page ... This is the place I would start...
Atomic Four Engine Service co. ... Great info and an excellent history of the A4
C&C Photo Album Site ... The excellent C&C Photo Album web site has PDF versions of the A4 owners manual and A4 service manual.
Moyer Marine ... Don Moyer is the world reknown A4 guru

Several 10M's have been re-powered over the years. Engines installed have included Universal, Westerbeke, Perkins and Yanmar. Barry Meehan (#168) wrote an article on the process of changing from an A4 to a Westerbeke in the Pearson Current Volume 4, #4 1998. The article can be found on the NPYOA website but you need to be a member for access.

I made a table comparing engines from several manufacturers. Most of the content is from Joe DeMers. Joe is a Beta Marine dealer and I think he was able to supply more complete information for the Beta engine in the table.
Engine Comparison Table
The engines in the table are in the 25-29 HP range. That may be more than needed in the 10M. Some additional research is needed.