Just got back from a trip, and glad to be able to post my translation:

En eftir um vorið kom Ingunn móðir Þórðar vestan af Skálmarnesi.
And after, during spring, Thor's mother Ingunn from the west of Skalmarness (Prong's-ness).

Hann tók vel við henni.
He received her well.

Hún kvaðst vilja ráðast undir áraburð Þórðar.
She stated for herself to become dependent on Thord. (Z. áraburðr - koma (ráðast) undir áraburð e-s, to become dependent on one)

Kvað hún Kotkel og konu hans og sonu gera sér óvært í fjárránum og fjölkynngi en hafa mikið traust af Hallsteini goða.
She said Kotkel and his wife and son become unpeaceful in robbery(?) and sorcery and have much protection from chief Hallstein.

Þórður veikst skjótt við þetta mál og kvaðst hafa skyldu rétt af þjófum þeim þótt Hallsteinn væri að móti, snarast þegar til ferðar við tíunda mann.
Thord stirred speedily with this case and stated for himself have duty precisely of the thieves thought Hallstein was against, hastens at once to a journey with nine men.

Ingunn fór og vestur með honum.
Ingunn also went west with him.

Hann hafði ferju úr Tjaldanesi.
He had traveled out of Tjaldanes (Tent-ness).

Síðan héldu þau vestur til Skálmarness.
Then they kept west to Skalmarness.

Þórður lét flytja til skips allt lausafé það er móðir hans átti þar en smala skyldi reka fyrir innan fjörðu.
Thord caused to move to a ship all the movable property that his mother owned there and (the) sheep (they) should drive inside of (the) inlet. (Z. fyrir innab., prep. with acc. Inside of, within)

Tólf voru þau alls á skipi.
They were twelve in all on the ship.

Þar var Ingunn og önnur kona.
Ingun was there and another woman.

Þórður kom til bæjar Kotkels með tíunda mann.
Thord come to Kotkel's farm with nine men.

Synir þeirra Kotkels voru eigi heima.
They, Kotkel's sons, were not at home.

Síðan stefndi hann þeim Kotkeli og Grímu og sonum þeirra um þjófnað og fjölkynngi og lét varða skóggang.
Then he cited them, Kotkel and Grim and their sons, for thievery and witchcraft and caused to defend outlawry (caused them to defend themselves against charges of outlawry?).

Hann stefndi sökum þeim til alþingis og fór til skips eftir það.
He summoned them on charges to the all-Thing and went on ship after that.

Þá komu þeir Hallbjörn og Stígandi heim er Þórður var kominn frá landi og þó skammt.
They, Hallbjorn and Stigand, then came home when Thord had come from land and nevertheless brief (?).

Sagði Kotkell þá sonum sínum hvað þar hafði í gerst.
Kotkell then told his sons what had happened there.

Þeir bræður urðu óðir við þetta og kváðu menn ekki hafa fyrr gengið í berhögg við þau um svo mikinn fjandskap.
The brothers became furious with this and said men hadn't previously entered into an open fight with them concerning so much hostility. (Z. berhögg, n. in the phrase, ganga í (or á) berhögg við e-n, to enter into open fight with)

Síðan lét Kotkell gera seiðhjall mikinn.
Then Kotkell caused to make a great incantation.

Þau færðust þar á upp öll.
They moved themselves all up there.

Þau kváðu þar fræði sín en það voru galdrar.
There they said his lore and that was sorcery.

Því næst laust á hríð mikilli.
Thereupon (they) were caught by a violent snow-storm. (Z. hríð (pl. -ir), f. (1) storm, esp. snowstorm; h. mikla gerði at þeim, laust á fyrir þeim h. mikilli, they were caught by a violent snow-storm)

Það fann Þórður Ingunnarson og hans förunautar þar sem hann var á sæ staddur og til hans var gert veðrið.
Thord, son of Ingunnar and his fellow travelers found that there was he was situated at sea and until the weather had passed him.

Keyrir skipið vestur fyrir Skálmarnes.
The ship is driven from the west before Skalmarness.

Þórður sýndi mikinn hraustleik í sæliði.
Thord showed much valor in help at sea.

Það sáu þeir menn er á landi voru að hann kastaði því öllu er til þunga var utan mönnum.
The men saw that, which on land was thrown thus all that was of weight, except for people.

Væntu þeir menn er á landi voru Þórði þá landtöku því að þá var af farið það sem skerjóttast var.
The men hoped for that to land was Thord then landing because then was gone from that as was sailed past.

Síðan reis boði skammt frá landi sá er engi maður mundi að fyrri hefði uppi verið og laust skipið svo að þegar horfði upp kjölurinn.
Then rose a messenger a short distance from land saw that no man would rather have lived so that at once the keel turned up (i.e., the boat capsized). (Z. uppi (2) vera, u., to live)

Þar drukknaði Þórður og allt föruneyti hans en skipið braut í spón og rak þar kjölinn er síðan heitir Kjalarey.
Thord and all his companions drowned there and the ship was dashed in pieces and the keel drifted there which later is called Kjalarey.

Skjöld Þórðar rak í þá ey er Skjaldarey er kölluð.
Thord's shield drifted to that island which is called Skjaldar-island.

Lík Þórðar rak þar þegar á land og hans förunauta.
Thord's and his companions' bodies drifted there at once to land.

Var þar haugur orpinn að líkum þeirra þar er síðan heitir Haugsnes.
A mound was raised there for their bodies, there which then is called Haug's-ness.